# Sleepy Princess in the Demon Castle

Sleepy Princess in the Demon Castle (Japanese: 魔王城でおやすみ, Hepburn: Maōjō de Oyasumi, lit. 'Good Night in the Demon King's Castle') is a Japanese manga series written and illustrated by Kagiji Kumanomata. It has been serialized in Shogakukan's shōnen manga magazine Weekly Shōnen Sunday magazine since May 2016, with its chapters collected in twenty-nine tankōbon volumes as of February 2025. An anime television series adaptation produced by Doga Kobo aired from October to December 2020.

## Plot

The story follows Princess Syalis, a young princess who was kidnapped by the Demon King, and her quest to sleep well while imprisoned. Despite the Demon King's best attempts, the princess turns her kidnapping into a vacation; having grown tired with the stress of a royal life, she is indifferent to the situation.

## Characters
### Princess Syalis (スヤリス姫, Suyarisu Hime)

    Voiced by: Inori Minase (Japanese); Kira Buckland (English)
    Princess Syalis (full name: Aurora Sya Lis Goodereste) (オーロラ・栖夜・リース・カイミーン, Ōrora Suya Rīsu Kaimīn) is a princess who was kidnapped by the demon king and causes chaos in the demon castle while trying to get a good night's sleep. She has been living at the demon king's castle for a year now due to her wishing to escape the stresses of royal life and making no intention to escape. Before long, she begins accepting the demon castle as her new home.

### Twilight the Demon King (魔王タソガレ, Maō Tasogare)

    Voiced by: Yoshitsugu Matsuoka (Japanese); Alejandro Saab (English)
    The leader of the demon race, who is also the one responsible for abducting Syalis. He is usually annoyed by her antics and sometimes get dragged into them. Despite being the Demon Lord, he's not all that intimidating or ruthless.

### Demon Cleric (あくましゅうどうし, Akuma Shūdōshi)

    Voiced by: Kaito Ishikawa (Japanese); Mike Haimoto (English)
    A demon priest who has the power to bring those who were killed back to life. Most of the time, he had to revive Syalis after she accidentally kills herself or those that she killed for her own means. Like Twilight, he also sometimes gets dragged into Syalis's antics. He seems to have feelings for Syalis as he gets very jealous when anyone else has feelings for her.

### Dawner the Hero (勇者アカツキ, Yūsha Akatsuki)

    Voiced by: Hiro Shimono (Japanese); Nicholas Andrew Louie, Bryn Apprill (young) (English)
    Dawner is the hero who is entrusted by the Human Confederation of Goodereste with the task of saving Princess Syalis from the demon castle. Although Dawner and Princess Sylias are childhood friends and also engaged, she does not remember who he is. Whenever she mentions Dawner to the denizens of the demon castle, she calls him, "Daw-What's-His-Name". Due to Dawner being outgoing and friendly to Princess Syalis, yet being incredibly clumsy and prone to mistakes, he had always annoyed her, thus causing her to have nightmares when at one point he enters her dreams. He is also known for his poor sense of direction, which explains why Princess Syalis has been captured for a year, along with Syalis' unwillingness to escape.

### Quilladillo (はりとげマジロ, Hari Toge Majiro)

    Voiced by: Rikiya Koyama (Japanese); Ben Lepley (English)
    One of Twilight's henchmen. He resembles a porcupine.

### Frankenzombie (フランケンゾンビ, Furankenzonbi)

    Voiced by: Kōichi Sōma (Japanese); Jim Foronda (English)
    One of Twilight's henchmen. He resembles Frankenstein.

### Minotaur (ミノタウロス, Minotaurosu)

    Voiced by: Masashi Yamane (Japanese); Gianni Matragrano (English)
    One of Twilight's henchmen.

### Castle Goblin Grunt (やしき手下ゴブリン, Yashiki Teshita Goburin)

    Voiced by: Shinya Takahashi (Japanese); Ricco Fajardo (English)
    One of Twilight's henchmen.

### Great Red Siberian (レッドシベリアン・改, Reddo Shiberian-Kai)

    Voiced by: Chikahiro Kobayashi (Japanese); J. Michael Tatum (English)
    Loyal retainer to the Demon Lord, in charge of enforcing rules. The princess drives him batty by her blatant disregard to the fact she's supposed to be a hostage. In fact, later in the series, he notes that Princess is costing them a fortune with all her misadventures; adding onto the woe everyone endures.

### Monster Shroud (おばけふろしき, Obake Furoshiki)

    Voiced by: Kōichi Sōma (Japanese); Bryce Papenbrook (English)
    He and his subordinates are the principal victims of Princess Syralis's antics, especially when she needs cloth to make things to get a good sleep. The death of the Ghost Shrouds by the Princess is a common joke in the series.

### Ghost Shrouds

    Monster Shroud's minions.

### Poseidon (ポセイドン)

    Voiced by: Takeo Ōtsuka (Japanese); Kevin Thelwell (English)
    A demon who has dominion over water. Because Poseidon never wears a shirt, the princess labels him a nudist.

### Fire Venom Dragon (かえんどくりゅう, Kaen doku Ryū)

    Voiced by: Takaya Kuroda (Japanese); Jason Marnocha (English)
    A demon who has dominion over fire. He always wears a mask.

### Neo Alraune (ネオアルラウネ, Neo Aruraune)

    Voiced by: Sayaka Ohara (Japanese); Michele Knotz (English)
    A gentle plant demon, whom has motherly concern for the Princess. While willing to overlook all the deaths the Cleric is forced to undo, Neo Alraune became "miffed" upon realizing her tree trunk brother killed by the Princess as part of one her usual ridiculous sleep plans.

### Alazif (アラージフ, Arājifu)

    Voiced by: Ayane Sakura (Japanese); Suzie Yeung (English)
    Spirit of a forbidden grimoire the princess freed by sheer dumb luck. Alazif tries encouraging Syalis to use his powers to defeat the demons and leave the castle; however, she is left severely disappointed with her due to her preoccupation with sleeping.

### Scissors Sorcerer (シザーマジシャン, Shizā Majishan)

    Voiced by: Junichi Suwabe (Japanese); Kyle Igneczi (English)
    A demon with an arm made of scissors. Syalis gave him her crown to keep his arm together in exchange for his lost scissors; unfortunately, leading to her routine of killing the ghost shrouds.

### Gearbolt

    A scientist demon.

### Harpy (ハーピィ, Hāpī)

    Voiced by: Ayaka Ōhashi (Japanese); Morgan Garrett (English)
    A harpy who believes that the princess considers her a friend over a misunderstanding with Syalis wishing to nap on Harpy's feathers.

### Hades (ハデス, Hadesu)

    Voiced by: Kishō Taniyama (Japanese); Christopher Wehkamp (English)
    Poseidon's older brother. Hades is always looking for chance to usurp the throne if Twilight messes up bad enough because of their mutual grudge.

### Hypnos (睡魔, Suima)

    Voiced by: Shin-ichiro Miki (Japanese); Robbie Daymond (English)
    A sleep demon; he must sleep 20 hours a day or risk death. Hypnos was called to examine Syalis' nightmare at one point; revealing to the demons just how much the princess detests Dawner (the source of the nightmare).

### Bussy/Cubey (さっきゅん, Sakkyun)

    Voiced by: Ari Ozawa (Japanese); Jad Saxton (English)
    A succubus who looks eerily like the princess; only she has purple hair and gold eyes. Cubey wished to learn why the princess was so popular despite looking the same, but got sucked into being trained as her double.

### Queen Nemlis (カイミーンの女王, Kaimīn no Joō)

    Voiced by: Saori Hayami (Japanese); Elizabeth Maxwell (English)
    Nemlis (full name: Aurora Nem Lis Goodereste) (オーロラ・音無（ネム）・リース・カイミーン, Ōrora Nemu Rīsu Kaimīn) is the queen of Goodereste, a kingdom of humankind, and mother of Princess Syalis.

### Teddy Demons

    Living teddy bears with wings. Syalis keeps one as a pet and bribes them into giving her the keys to her cell in exchange for being brushed. They soon develop a good relationship with her.

### Morgan

    A muscular paladin who works in Goodereste's castle.

### Evening Star

    A paladin who works in Goodereste's castle. He is only awake at night and falls asleep when its daytime.

### Ker, Ber, and Ros

    Hades' subordinates. They are a trio of wolf demons.

### Tire Genie

    A demon whose body is made of tires. Should his body be missing, he appears in gaseous form.

### Ice Golem

    A demon made of ice cubes. He is the leader of the ice demons.

### Neo Alraune's older brother.

    Neo's unnamed older brother who is a demon that resembles a tree stump. Even when his body is cut up, he does not die so easily.

## Media
### Manga

Written and illustrated by Kagiji Kumanomata, Sleepy Princess in the Demon Castle started in Shogakukan's shōnen manga magazine Weekly Shōnen Sunday on May 11, 2016. Shogakukan has collected its chapters into individual tankōbon volumes. The first volume was released on September 16, 2016. As of February 18, 2025, twenty-nine volumes have been released.
Viz Media announced in September 2017 that they had licensed the series in North America. The first volume was released on June 12, 2018. On May 9, 2023, Viz Media launched their Viz Manga digital manga service, with the series' chapters receiving simultaneous English publication in North America as they are released in Japan.
An official fanbook of the series was released on October 16, 2020.

#### Volumes

| No. | Original release date | Original ISBN | English release date | English ISBN |
| 1 | September 16, 2016 | 978-4-09-127342-0 | June 12, 2018 | 978-1-9747-0018-9 |
| "Castle of the Sleepy Princess" (シーツは輝く海のように, Shītsu wa Kagayaku Umi no Yō ni)"Bedsheets Like the Shining Sea" (うなれ筋肉, Unare Kinniku)"Sweet Sleep Like the Dead" (死という甘い眠り, Shi to iu Amai Nemuri)"Longing to Sleep on the Shield of the Wind" (風の盾で寝るしか, Kaze no Tate de Neru Shika)"Because the Tower is There" (そこに塔があるから, Soko ni Tō ga aru kara)"Go Bark at the Moon" (月にでも吠えていろ, Tsuki ni demo hoete iro)"The Poisonous Mushroom of Dreams" (夢みる毒キノコ, Yumemiru Doku Kinoko)"The Princess's Three-Star Armor" (姫の三ツ星機甲, Hime no Mitsuboshi Kikō)"But You Have to Pay the Price, Right?" (でも、お高い代償なんでしょう？, Demo, Okai Daishō nandeshō?)"Good Night, Baby" (ねむれよいこよ, Nemure yo Iko yo)"Touch Her and She's Yours" (触れば落ちぬ, Sawareba Ochinu)"The Sea of Pillows and the Tower of Babel" (枕の海とバベルの塔, Makura no Umi to Baberu no Tō)"Sacred Treasure Crossing: Wild World" (おいでよ神器の森, Oide yo Jingi no Mori) |||||
| 2 | January 18, 2017 | 978-4-09-127488-5 | August 14, 2018 | 978-1-9747-0713-3 |
| "The Mysterious Case of the Hot Springs Steam Monster Murders" (ゆけむり殺魔物, Yukemuri Ya Mamono)"The Pale Brute" (白い凶人, Shiroi Kyōjin)"Princess Stuff It" (しまっちゃう姫様, Shimacchau Hime-sama)"It Looks like a Princess and Has the Brain of a Princess" (見た目は姫 頭脳も姫, Mita Me wa Hime Zunō mo Hime)"Comforter = Friend" (布団, Tomodachi)"Extreme Training Tournament of Monsters" (ドキッ！魔物だらけの修練大会, Doki! Mamono Darake no Shūren Taikai)"The Bloom Quickly Fades from the Flower" (花の命は短くて, Hana no Inochi wa Mijikakute)"Squeezing Honey out of Nothing?" (なぜ蜂蜜は無から生まれないの, Naze Hachimitsu wa Nakara Umarenai no)"The Guardian of Quality Sleep" (安眠の番人, An'min no Ban'nin)"See You Tonight" (今夜、会いに行さます, Kon'nya, Ai ni Gyo Samasu)"My Way of Laundry" (我が道のお洗湿, Wagamichi no O Arai Shime)"From Cradle to Grave" (揺りかごで墓場まで, Yurikago de Hakaba Made)"Demon Castle Paralysis" (魔王城（金）縛りプレィ, Maō-jō (kin) Shibari Purei) |||||
| 3 | April 18, 2017 | 978-4-09-127560-8 | October 9, 2018 | 978-1-9747-0020-2 |
| "Sloth Generator" (なまけもの製造機, Namakemo no Seizouki)"Fluffy Comforter Taxi" (ゆるふわ布団タクシー, Yurufuwa Futon Takushī)"The Princess's Undergarments" (姫のばんつはイイパンツ, Hime no Bantsu wa Ii Pantsu)"Let's Remodel Your Window!" (窓をアップデートできます!, Mado o Appudēto Dekimasu!)"It's Not That Bad Getting Fused with a Cat, Is It?" (猫と混ざってもいいんじゃないッ?, Neko to Mazatte mo īn Janaī?)"Naughty or Nice Princess" (ひめはわるいこだから, Hime wa Warui Kodakara)"Don't Take Party Games Too Seriously!" (パーティーゲームに本気になるのやめろよ!, Pātīgēmu ni Honkininaru no Yamero yo!)"Puffy Princess" (もちもち♡プリンセス, Mochi Mochi♡Purinsesu)"Sleeping Out on the Demon Castle Grounds" (魔王城周辺でおやすみ, Maō-jō Shūhen de Oyasumi)"The Divine Move in Her Dreams" (神の一手インドリーム, Kami no Itte Indorīmu)"The Perfect Happy Hostage" (完壁で幸福な人質, Kan Kabe de Kōfukuna Hitojichi)"Demon King - Sleep or Die" (魔王様スリープオアダイ, Maō-sama Surīpu Oa Dai)"You Mustn't Hide It" (隠すなんてょくないよ, Kakusu Nante Yokunai yo) |||||
| 4 | July 18, 2017 | 978-4-09-127669-8 | December 11, 2018 | 978-1-9747-0148-3 |
| "Chocolate is the Color of Love" (チョコは血の色愛の色, Choko wa Chi no Iro Ai no Iro)"Quilly Doesn't Hibernate" (とげちゃんは眠らない, Toge-chan wa Nemuranai)"Who's Been Sleeping Too Much?" (ねすぎるこだれだ, Ne Sugiru ko Dareda)"Attack of the Teddy Demon Subspecies!" (強襲!! でびあくま亜種, Kyōshū!! Debi Akuma Ashu)"Let's Have a Sing-Along" (つくってうたお, Tsukette Utao)"The Princess Goes Demon Castle Hopping" (魔王城をハシゴする女, Maō-jō o Hashigo Suru On'na)"It Seems There is a Specialist for Everything" (なんにでもプロっているんだね, Nan ni Demo Puro Tte Iru nda ne)"Retrieve the Princess (A Demon Castle Monster)" (姫（魔王城モンスター）なとりもどせ, Hime (Maō-jō Monsutā) na Torimodose)"Extreme Training Magic Tournament of Monsters" (ドキドキッ！ 魔物だらけの魔術大会, Dokidoki~tsu! Mamono Darake no Majutsu Taikai)"Better Living Through Gadgets" (便利グッズで一山当てたい, Benri Guzzu de Hitoyama Atetai)"The Princess Doesn't Only Dance at Meetings" (会議でなくとも姫は踊る, Kaigidenakutomo Hime wa Oduro)"Pollenella" (花粉かぶり姫, Kafun Kaburi Hime)"Not Fair Play!" (その攻略法ズルだと思います, Sono Kōryaku-hō Zuruda to Omoimasu) Bonus Chapter: "Sleepy Princess in Komi's House" (古見さんちでおやすみ, Komi-san Chi de Oyasumi) Bonus Chapter: "Not Everything That Looks Tasty Is..." (差し入れとみせかけて, Sashiire to Misekakete) |||||
| 5 | October 18, 2017 | 978-4-09-127860-9 | February 12, 2019 | 978-1-9747-0149-0 |
| ""Rockin' Till the Break of Daw-What's-His-Name"" (春眠アなんとかを覚えず, Shunmin a Nantoka o Oboezu)"It's Like Female Bonding" (それは女の友情のように, Sora wa On'na no Yūjō no Yō ni)"The Princess's Marvelous Pillow Boutique" (姫のすてきなまくらやさん♡, Hime no Sutekina Makura Ya-san ♡)"The Secret Garden at the End of Endurance" (ガマンの先の花園, Gaman no Saki no Hanazono)"No One Did Anything Wrong" (だあれもわるくないよ♡, Da Are mo Warukunai yo ♡)"From the Mouths of Princesses" (姫のびんかんなおくち, Hime no Bin Kan'na o Kuchi)"Supersize My Demon Castle" (びんかんスーパーサイズfor魔王城, Bin Kan Sūpāsaizu fō Maō-jō)"No Fair Calling in a Grown-Up!" (大人呼ぶのは反則だろうが, Otona Yobu no wa Hansokudarouga)"Radically Transforming Giant Eggplant Seal" (劇変!ビッグナスあざらし, Gekihen! Biggunasu Azarashi)"Togetherness with Big Sister Syalis" (すやりすお姉ちゃんといっしょ, Suya Risu o Nēchan to Issho)"Don't Look Away" (その瞳をそらさないで, Sono Hitomi o Sorasanaide)"Full-Time Sweatshop Princess" (プラックフルタイムひめさま, Purakkufurutaimu Hime-sama)"One Person's Mistake Is Not Another's Lesson" (人のふり見てわがふりなおすと思うのかよ, Hito no Furi Mite Waga Furi Naosu to Omou no ka yo) |||||
| 6 | January 18, 2018 | 978-4-09-128073-2 | April 9, 2019 | 978-1-9747-0227-5 |
| 7 | April 12, 2018 | 978-4-09-128227-9 | June 11, 2019 | 978-1-9747-0514-6 |
| 8 | August 17, 2018 | 978-4-09-128381-8 | August 13, 2019 | 978-1-9747-0783-6 |
| 9 | November 16, 2018 | 978-4-09-128577-5 | October 8, 2019 | 978-1-9747-0881-9 |
| 10 | February 18, 2019 | 978-4-09-128801-1 | December 10, 2019 | 978-1-9747-0960-1 |
| 11 | May 17, 2019 | 978-4-09-129157-8 | April 14, 2020 | 978-1-9747-1261-8 |
| 12 | September 18, 2019 | 978-4-09-129332-9 | June 9, 2020 | 978-1-9747-1539-8 |
| 13 | January 17, 2020 | 978-4-09-129546-0 | October 13, 2020 | 978-1-9747-1817-7 |
| 14 | April 16, 2020 | 978-4-09-129563-7 | April 13, 2021 | 978-1-9747-1980-8 |
| 15 | July 17, 2020 | 978-4-09-850162-5 | August 10, 2021 | 978-1-9747-2365-2 |
| 16 | October 16, 2020 | 978-4-09-850270-7 | December 14, 2021 | 978-1-9747-2409-3 |
| 17 | December 18, 2020 | 978-4-09-850366-7 | April 12, 2022 | 978-1-9747-2539-7 |
| 18 | May 18, 2021 | 978-4-09-850525-8 | July 19, 2022 | 978-1-9747-3101-5 |
| 19 | August 18, 2021 | 978-4-09-850640-8 | November 8, 2022 | 978-1-9747-3229-6 |
| 20 | November 18, 2021 | 978-4-09-850729-0 | April 11, 2023 | 978-1-9747-3423-8 |
| 21 | March 17, 2022 | 978-4-09-850869-3 | August 8, 2023 | 978-1-9747-3637-9 |
| 22 | June 17, 2022 | 978-4-09-851146-4 | November 14, 2023 | 978-1-9747-4132-8 |
| 23 | October 18, 2022 | 978-4-09-851346-8 | February 13, 2024 | 978-1-9747-4309-4 |
| 24 | March 16, 2023 | 978-4-09-851772-5 | June 11, 2024 | 978-1-9747-4568-5 |
| 25 | July 18, 2023 | 978-4-09-852613-0 | August 13, 2024 | 978-1-9747-4635-4 |
| 26 | November 17, 2023 | 978-4-09-853013-7 | October 8, 2024 | 978-1-9747-4913-3 |
| 27 | March 18, 2024 | 978-4-09-853177-6 | March 11, 2025 | 978-1-9747-5253-9 |
| 28 | September 18, 2024 | 978-4-09-853573-6 | — | — |
| 29 | February 18, 2025 | 978-4-09-854008-2 | — | — |

### Anime

An anime television series adaptation was announced in Weekly Shōnen Sunday in September 2019. The series was animated by Doga Kobo and directed by Mitsue Yamazaki, with Yoshiko Nakamura handling series composition and Ai Kikuchi designing the characters. Yukari Hashimoto composed the series' music. The series ran for 12 episodes from October 6 to December 22, 2020, on TV Tokyo, AT-X, and BS TV Tokyo. Inori Minase performed the opening theme "Kaimin! Anmin! Syalist Seikatsu" (快眠！安眠！スヤリスト生活, "Sleep! A Good Night's Sleep! Syalist Life"), while ORESAMA performed the ending theme "Gimmme!".
Funimation acquired the series and streamed it on its website in North America and the British Isles. On February 21, 2021, Funimation announced the series would receive an English dub, with the first episode premiering the next day. Following Sony's acquisition of Crunchyroll, the series was moved to Crunchyroll. In Southeast Asia and South Asia, the anime is licensed by Muse Communication, and released on Bilibili in Southeast Asia. The series premiered on Animax Asia on May 12, 2021.

#### Episodes

| No. | Title | Directed by | Written by | Original release date |
| 1 | "Sleepless Princess of the Castle" Transliteration: "Nemurenu Shiro no Hime" (Japanese: 眠れぬ城の姫) | Mitsue Yamazaki | Yoshiko Nakamura | October 6, 2020 (2020-10-06) |
| Twilight the Demon King attacks the human kingdom of Goodereste and abducts Princess Syalis, demanding that they surrender their lands in exchange for her return. The people worry for the princess, and a hero named Dawner sets off to rescue her. At the Demon Castle, Syalis is locked in a cell; however, she has no plans to escape as she wishes to escape the stresses of her royal life and only cares about wanting to sleep. Realizing how uncomfortable her pillow is, she notices some Teddy Demons bringing her a meal and she at first considers killing them to get their fluff, she changes her mind and instead decides to brush them in exchange for it and discovers that she can use this method to bribe them for the cell keys should she need to get out. After taking some of Quilladillo's quills and some herbs from the item storage, she is able to make a better pillow. She next decides to get a more comfortable headband and when Scissors Sorcerer visits with a meal, she trades her crown to him to help keep his scissors-made arm together in exchange for some of his scissors, which she uses to make a new headband. Now wanting a new bedsheet, she leaves her cell and uses a giant pair of scissors that she got from Scissors Sorcerer to look for the right kind of cloth around the castle, eventually getting it from a Ghost Shroud. Unable to sleep due to loud noise around the castle, she goes to the treasury and removes a wind amulet from a shield using a sentient jewel who guards the area. As she walks through a lava area, she slips on a slime and falls into the lava, but is revived by a demon priest named Cleric, who owns the Demon Church that lies beneath the castle. Deciding to use the coffin as a makeshift bed that can block out noise, she uses his horns to refine it and uses the same slime from before to wax it. Once done, she climbs inside it to sleep as she is then carried back to her cell. Twilight learns of her actions and tries to talk to her, but his every attempt is stopped due to her being asleep at those times. Meanwhile, Dawner's attempts to rescue Syalis grow more and more difficult due to how powerful Twilight's forces are. |||||
| 2 | "The Princess and Furious Fluff" Transliteration: "Hime to Ikari no Mofumofu" (Japanese: 姫と怒りのモフモフ) | Sumie Noro | Yoshiko Nakamura | October 13, 2020 (2020-10-13) |
| Dawner and his party are trying to get through a labyrinth, but are confronted by Twilight, who leaves after taunting them. They eventually escape, only to confront a Sand Dragon. Because of how powerful it is, Dawner had to retreat. Back at the castle, Syalis grows annoyed by all the bugs in the area and decides to make a mosquito net. She is confronted by the Monster Shroud, the leader of the Ghost Shrouds, for cutting of his minions, but he himself gets cut by her to make the cloth for the net. Making string from the cloth, she decides to tie it to a nearby Phoenix nest to keep it up and tricks a Stamp Cat into taking off his shoes that allow him to walk on walls so she can use them to climb up to the nest. Twilight learns of this and, believing that she is trying to help Dawner, goes with his minions to stop her, but to their surprise, she didn't take any of the eggs at all and instead ties the string to the nest; its power causes her bug bites to disappear. She then returns to her cell to sleep, having finished making the mosquito net, which is now powered by the eggs. Syalis later takes a sleeping potion from a meeting, but when it doesn't work on her, she tries sleeping on some mushrooms, unaware that they are poisonous. Cleric had to revive her again as she had accidentally killed herself many times before. She later tries taking a sleeping potion from the item storage, but is exposed by Great Red Siberian, Twilight's stein retainer, who takes her back to her cell and upon learning of her actions, makes her return what she has taken, except for Teddy Demon that she adapted as a pet. When she falls asleep during his lectures, he grows increasingly frustrated and considers cutting off his beard due to her liking to sleep on it, but Twilight insists that he doesn't. |||||
| 3 | "The Princess and Forbidden Knowledge" Transliteration: "Hime to Kindan no Arekore" (Japanese: 姫と禁断の叡智) | Mariachi Hug Yu | Yoshiko Nakamura | October 20, 2020 (2020-10-20) |
| Upon learning of grimoires hidden in the castle, Syalis sneaks into the library to find a grimoire to read so she can sleep and accidentally opens a grimoire that contains a spirit named Alazif, who hopes that she will use her to destroy the demons, but she is not interested and instead wants to sleep. Alazif agrees to teach Syalis a sleep spell, but it puts everyone to sleep except for them. Alazif gets frustrated when Syalis chooses to instead use the grimoires as a makeshift bed rather than use this time to escape, but nevertheless supports her. Still unable to sleep, Syalis decides that she needs someone to push her pressure points to sleep and has a Teddy Demon do it. When it doesn't work, she asks around for someone who can and Twilight ends up doing the job. Later, due to the castle being in an eternal nighttime, Syalis desires sunlight and notices something glowing in the forest and heads off there. After she manages to escape the castle despite the dangerous traps that were set up to prevent her from doing so, the castle inhabitants realize that she is going after Twilight's ultimate weapon and may again be planning to help the hero. She eventually finds the weapon, a glowing sword. As the demons prepare to look for Syalis, they are shocked to see her heading back to the castle with the weapon willingly. Once back in her cell, she uses the sword and a cloth to create a makeshift sun, allowing her to sleep better. Meanwhile, Dawner and his party are still progressing to the Demon Castle. |||||
| 4 | "The Princess, Destruction, and a Short Journey" Transliteration: "Hime to Hakai to Chīsana Bōken" (Japanese: 姫と破壊と小さな冒険) | Geisei Morita | Michihiro Tsuchiya | October 27, 2020 (2020-10-27) |
| While taking a bath in green water, her tub breaks due to it being too small for her. She goes to the public baths and rediverts the water to her cell. Still lacking a larger tub, she blows up a Rocket Turtle so she can use its shell as a makeshift tub. Great punishes her for this by having her put the turtle back together. When the temperature gets too high, Syalis finds herself unable to sleep. Upon noticing some ice demons rebelling against fire demons, she decides to go to the Ice Area and uses Tire Genie's body to protect herself from the cold, leaving the latter as a gaseous being, but she gets mistaken for the Ice Golem, the leader of the ice demons. She nevertheless tricks them into building an igloo inside her cell using the real Ice Golem's body while proving cold air for her. Great again punishes her by having reassemble Ice Golem. While on her way back to her cell with an item, Syalis accidentally shrinks herself after finding an hourglass-like artificial. She is unable to carry her things and when the inhabitants begin playing with her while she desperately tries to get them to take her back to her room and she ends up falling asleep. She returns to normal later after. |||||
| 5 | "The Princess and Female Warriors" Transliteration: "Hime to Tatakau On'na-tachi" (Japanese: 姫と戦う女たち) | Sumie Noro, Takaharu Ōkuma | Yoshiko Nakamura | November 3, 2020 (2020-11-03) |
| A group of female demons return from the war against the humans. A young harpy named Harpy wants to befriend Syalis, but struggles to do so. Syalis eventually agrees to become her friend just so she can use her wings as comforters. Wanting a more comfortable mattress, she gets Harpy to carry her to the castle's giant horns, which are actually soft. She then cuts the horns open to get the fluff out before returning to her cell and spending the night sleeping with Harpy. Syalis later returns the fluff to Twilight. Meanwhile, Dawner's group have finally managed to defeat the Sand Dragon. Learning of this, Twilight arranges a meeting with his fellow demons. When Syalis disrupts them with her antics, she is sent away by Great. They witness her cut up Neo Alraune's tree stump-like big brother to use a makeshift bed, though he is unharmed. Neo visits Syalis the next day. |||||
| 6 | "The Princess' Unwavering Choice" Transliteration: "Hime no Mayoi Naki Sentaku" (Japanese: 姫の迷いなき選択) | Tatsuya Nokimori | Michihiro Tsuchiya | November 10, 2020 (2020-11-10) |
| Dawner's party comes across three paths leading into caves, but they are all traps. After staining her bedsheet, Syalis attempts to find a way to clean it. Meanwhile, Twilight learns that the hero has a poor sense of direction and decides to help him out. An inventor demon named Professor Gearbolt proposes an idea. Syalis uses water from an underwater fountain and a bubble soldier as soap to wash her bedsheet. She then uses a magnetic staff and Gearbolt's robot as a dryer. Although it was able to dry the bedsheet, it also destroys the robot. Once Gearbolt shows it to the group, they find it wrecked and Syalis sleeping. Great had to again punish Syalis for her actions as Gearbolt gets to work on a new robot. Syalis later wants to make woolen underwear, but after remembering that showing it off when she was young was inappropriate, she tries to do it without anyone knowing, but this makes the inhabitants think that she's up to no good. She eventually succeeds in her task. Gearbolt has redesigned his new robot to resemble Syalis. After Twilight learns of Syalis's presumed attack scheme, he checks on her, only to find her sleeping. Syalis is still unable to fall asleep and after seeing Twilight tired from work, she tries to help him fall asleep, but does more harm than good. She eventually remembers how her mother used to put her to sleep by patting her and she uses this method to put Twilight to sleep for good while also falling asleep herself. The Teddy Demons then take her back to her room. Meanwhile, the hero has ended up back at Goodereste while Gearbolt's mech was left unencountered. |||||
| 7 | "Even More Sleepless Princess of the Castle" Transliteration: "Motto Nemurenu Shiro no Hime" (Japanese: もっと眠れぬ城の姫) | Yoshiyuki Shirahata, Mitsue Yamazaki, Sumie Noro | Yoshiko Nakamura | November 17, 2020 (2020-11-17) |
| Syalis is abducted from her cell and Twilight learns that she was kidnapped by Hades, Poseidon's brother. Poseidon then leaves, not wanting to be involved. Twilight learns that he plans to use Syalis as a means to obtain the throne. Syalis is unbothered by Hades' threats, as she still desires to sleep, but now has to redo her bed. She escapes her cell and threatens Hades' underlings Ker, Ber, and Ros into helping her. While Twilight's group speaks with Hades through a communication screen, Syalis steals his clothes while Twilight had to distract him to keep him from noticing, making their conversation awkward. Syalis finishes making her new pillow while Hades is angered that his clothes are missing. Also needing to redesign her bed, she gets past some booby traps and meets Hypnos, a demon who must sleep on most occasions to avoid death. She then requests sleeping advice from him. After disabling the traps' power source, Syalis figures out a way to convert the traps into a makeshift bed. Meanwhile, Twilight and his underlings mount a rescue, bringing along stuff to comfort Syalis. The princess then wakes up in a room full of coats. She then takes some of the coats and things from a magician's workshop to make another makeshift bed. Twilight confronts Hades, but after they notice Syalis escaping on her makeshift flying bed and heading back to the demon castle, they had to cancel the battle and follow her back. She again resumes sleeping in her cell. |||||
| 8 | "The Princess and the Frightful Demon Nightmare" Transliteration: "Hime to Mazoku no Osorubeki Akumu" (Japanese: 姫と魔族の恐るべき悪夢) | Geisei Morita | Michihiro Tsuchiya | November 24, 2020 (2020-11-24) |
| One of Dawner's men is able to open a small portal that allows him to reach Syalis, but it is not wide enough and Dawner ends up poking Syalis' head while she's sleeping. Eventually, the energy runs out and he is unable to conjure it again. Dawner nevertheless vows to save Syalis. Learning of the hero's actions, Twilight begins another meeting and sends Fire Venom Dragon to deal with him. Syalis interrupts the meeting and tells them about her nightmare regarding her childhood friend, who is revealed to be Dawner and is known to be quite clumsy, but she doesn't remember his name. She also reveals that they were engaged before returning to her cell to get some sleep. Cleric realizes who her childhood friend was and orders Fire to eliminate Dawner for good. After gaining cavities, the demons take her to a dentist, but she refuses to open her mouth as she finds it embarrassing. Teddy Demon is able to help with the situation and cure her cavities, to which she then falls asleep. Dawner's party later battle Fire, but the items Fire had were anything but helpful, resulting in his defeat. It turns out Twilight and his subordinates unknowingly swapped his items due to Syalis' interference, though they blame Syalis for this. This forces the demons to stop Fire from attacking Syalis as Dawner's group continue their journey. |||||
| 9 | "The Princess and Hostage Training Week" Transliteration: "Hime to Hitojichi Kyōka Shūkan" (Japanese: 姫と人質強化週間) | Hitomi Ezoe | Michihiro Tsuchiya | December 1, 2020 (2020-12-01) |
| While watching TV, Syalis considers buying a water bed, but fails to order one. She then decides to make one instead. The demons grow frustrated with Syalis' actions and decide to treat her like a hostage by ignoring her. As Syalis begins gathering things to make her water bed, the demons have difficulty trying to ignore her, eventually resulting in them being forced to help her. The demons then try another idea and after receiving unintentional advice from Hades, they decide to force her to work, but this also fails when she ends up finishing all the paperwork in one day. After capturing human bandits, Twilight decides to use them to show Syalis how a hostage is supposed to behave. She agrees to act like a hostage, but takes it too seriously, resulting in another defeat for the demons, though she still maintains her damsel act. Later at night, Syalis wonders why humans and demons fight. |||||
| 10 | "The Princess in Endopolis" Transliteration: "Hime to Owarino Shiti" (Japanese: 姫とオワリノシティ) | Tatsuya Nokimori | Yoshiko Nakamura | December 8, 2020 (2020-12-08) |
| Desiring a new product, Syalis breaks out of the castle to get it. The demons learn of this and after some difficulties, they manage to catch her using a bed in a cage. After she explains that she only wishes to visit the human town to get a new massage pillow, they reluctantly agree to help her and take disguises to hide from humans. After many antics in the human fair, Syalis ends up falling asleep again. They eventually manage to get the pillow and watch the fireworks, but Syalis has trouble sleeping. They return to the demon castle while carrying a sleeping Syalis. The next day, Syalis gives the massage pillow to the Teddy Demons to try while Noa and Posidon enjoy the souvenirs they brought back from the fair. |||||
| 11 | "The Princess and Troubling Dreams" Transliteration: "Hime no Nemurenai Yume" (Japanese: 姫の眠れない夢) | Sumie Noro | Michihiro Tsuchiya | December 15, 2020 (2020-12-15) |
| After Twilight learns that the hero is getting close to an area that is under construction, he leaves to warn the hero to take the left path after his party comes across a fork in the road, though Dawner is skeptical. Harpy visits Syalis and she decides to throw a pajama party. Syalis then visits Twilight for a practice pajama party, which does not go well and also leads Cleric to attack Twilight out of jealousy. As a result, Syalis had to cancel the party. Bussy, a succubus who looks identical to Syalis, wishes to be as popular as Syalis and tries to have the princess train her to be just like her, but Syalis instead has plans to make Bussy, whom she had renamed Cubey, a body double. Cubey finds her training too violent, which at one point results in Syalis landing in lava and forcing Cleric to revive her. Sometime later, Syalis cannot fall asleep due to nightmares and the demons get Hypnos to help. Reading her dreams, they learn of her past confrontations with Dawner and that she was trying to ignore him throughout her childhood. Twilight realizes that he had unknowingly left a spell called the Dream Travel Slip behind to be found by Dawner, which causes him to appear Syalis's dreams when she signed it. After Twilight retrieves it, Syalis is able to finally sleep peacefully and is taken back to her cell by the Teddy Demons. Twilight then decides to upgrade the area that's under construction to a super hard mode. Syalis wakes up to find cake left for her. |||||
| 12 | "Sleeping Princess of the Demon Castle" Transliteration: "Maōjō no Nemuri Hime" (Japanese: 魔王城の眠り姫) | Mitsue Yamazaki, Sumie Noro | Yoshiko Nakamura | December 22, 2020 (2020-12-22) |
| Christmas arrives and Syalis desires to see Santa Claus come, though Twilight is not willing to allow this. They learn from a letter that she wrote for Santa that she wishes to go back home. Syalis explains that the true reason why she wants to go back home is to retrieve some woolen underwear from her room. Twilight and Cleric reluctantly agree to help on the condition that they return to the demon castle after they are done and teleport to her bedroom in Goodereste. Upon hearing Syalis's mother Queen Nemlis approaching, the group quickly hide in a closet as Nemlis finds Cubey in her daughter's bed; Cleric brought her in case of an emergency. Despite being a demon, Nemlis believes that Cubey is her kidnapped daughter and takes her out to reveal to the kingdom of the princess's apparent return. Knowing that this is bad news to them, the group attempt to find a way to rescue her. They narrowly avoid a paladin named Morgan. Another paladin named Evening Star also learns of their presence and vows to catch them. They disguise themselves as Morgan to trick Evening Star. When he shares Syalis's childhood stories, it makes her uncomfortable as Twilight and Cleric try to keep her under control, eventually resulting in their cover being blown. However, Evening Star falls asleep when the sun comes out while chasing them, which is his known weakness. Remembering that they still need to rescue Cubey, Syalis puts her plan in motion as Nemlis announces to the public that her daughter has returned, unaware that who's with her isn't Syalis. Dawner's party has also made their return to the kingdom to witness the event. As the "princess" is asked to make an announcement regarding her experience, the real princess helps Cubey make her speech while in disguise while Twilight and Cleric prevent the nearby guards from interfering. Syalis then disguises herself as the Demon King and "abducts the princess" again, ordering her "minions" (Twilight and Cleric) to carry her and Cubey back to the demon castle. Dawner arrives too late to stop them. Nemlis recognizes her real daughter and is proud of her despite what has happened. Back at the castle, the demons celebrate Christmas, but had to go back to Goodereste to get the woolen underwear when they realize that they forgot them. Syalis shares them with the Teddy Demons before falling asleep once more. |||||

## Reception

In 2017, the series was ranked 16th at the third Next Manga Awards in the print category.
Anime News Network's staff included Sleepy Princess in the Demon Castle on their top 5 best anime list of 2020: Rebecca Silverman placed it at number four, praising the way the source manga gets cherry-picked and comes together as a whole, concluding that: "It's not only funny, but also one of the best adaptations I've seen, and I can't wait to start rewatching it as soon as it ends." Caitlin Moore placed it at number five, praising Mitsue Yamazaki and Yoshiko Nakamura for adapting "already funny source material, tweaking the jokes, and incorporating split-second comic timing to make it outright hilarious."