# Marriagetoxin

Marriagetoxin (Japanese: マリッジトキシン, Hepburn: Marijjitokishin, stylized as MARRIAGETOXIN) is a Japanese manga series written by Joumyaku and illustrated by Mizuki Yoda. It has been serialized on the mobile app and website of Shueisha's online magazine Shōnen Jump+ since April 2022, with its chapters collected in 12 tankōbon volumes as of February 2025. Viz Media licensed the series for English release.

## Plot summary

Hikaru Gero is a young man from the Poison Clan of professional assassins, which has been in existence for hundreds of years. Because he deals in the dark side of society and has never lived a "normal life", he considers himself to have no prospects with women and has no interest in marriage. However, one day, the Poison Clan states that if Gero does not marry and produce an heir to carry on their lineage, they will force his sister into bearing a child against her wishes. Wanting to save his younger sister from such a fate, Gero asks one of his assassination targets to marry him. When the cross-dressing marriage swindler Mei Kinosaki declines, Gero instead has Kinosaki train him to date and how to appeal to women with the goal of finding someone he truly wants to marry.

## Characters
### Protagonists
#### Hikaru Gero (下呂 ヒカル, Gero Hikaru)

    Voiced by: Kent Itō (PV)
    Gero is the designated heir of the Poison Clan, one of the Five Great Families of assassins.

#### Mei Kinosaki (城崎 メイ, Kinosaki Mei)

    Voiced by: Reina Ueda (PV)
    Kinosaki is a marriage swindler who has made countless men and women fall for them.

### Prospective partners
#### Kyoko Himekawa

    A thief who returns stolen art to its rightful owners.

#### Shiori Ureshino

    A college student who will one day take over her family's party supply company.

#### Kimie Arashiyama

    The Hamster Master, whose family is a branch subordinate to the Beast Clan.

### Friends
#### Piichi Nakagawa

    The Hit Man Hunter, an "ordinary guy" who has great talent with a knife. He wants to open a cafe with his girlfriend Marin and has decided to kill the assassins, starting with the Beast Clan, because he feels his potential patrons would not be able to dine in peace otherwise.

### Other Masters
#### Toshiro Dogo (Beast)

    Head of the Beast Clan and one of the Five Great Families. His animal partner species is a bat.

#### Tonako Dogo (Beast)

    New head of the Beast Clan and sister of Toshiro. Her animal partner species is a wolf.

#### Toshiki Hanamaki (Bug)

    His family is a branch subordinate to the Poison Clan. He is married to Anna Kawakita.

#### Tsunagi (Needle)

    His family is a branch subordinate to the Poison Clan.

#### Nagihiko Kushima (Spear)

    Killed by Piichi; he was infamous for indiscriminate killing.

#### Byakko (Bear)

    From a family subordinate to the Beast Clan which are shunned as the "impure masters" because they skin their bear partners rather than control them.

## Publication

Marriagetoxin is written by Joumyaku and illustrated by Mizuki Yoda. The manga was officially announced by Shueisha on April 11, 2022, and began its weekly serialization for free on the Shōnen Jump+ mobile app and website on the 20th of the same month. Shueisha also simultaneously publishes the series in English for free on the online platform and mobile app Manga Plus.
In June 2023, Viz Media announced that they licensed the series for English release under the name Marriage Toxin.

### Volumes

| No. | Original release date | Original ISBN | English release date | English ISBN |
| 1 | August 4, 2022 | 978-4-08-883213-5 | January 2, 2024 | 978-1-9747-4352-0 |
| "The Poison Master's Hunt For A Bride" (毒使いの婚活, Doku Tsukai no Kon Katsu)"Rough Around The Edges" (不束者ですが, Futsutsuka-sha de Suga)"What Is Charm, Anyway?" (魅力って何?, Miryokutte Nani?) "Commence Infiltration" (潜入開始, Sen'nyū Kaishi)"Dreams" (幻覚, Genkaku)"Thing I'd Be Willing To Trade My Life For" (命懸けても, Inochigakete mo) |||||
| Poison Clan Master Hikaru Gero is a killer with morals, targeting only what he calls "human scum", people who have ruined other people's lives; his emotional detachment makes him believe he must remain single, dooming the family line. However, after learning his friend, the Bug Master, has found love, and upon hearing his grandmother is forcing his younger sister Akari to marry against her wishes, he rescues his next target, Mei Kinosaki, rather than killing them. Kinosaki is a marriage swindler who has made countless men and women fall for them, and Gero asks them to help him find a wife. Initially, Gero's lack of personal charisma leads to numerous rejections, but after rescuing Kinosaki from a kidnapper, they realize his charm lies in his assassin talents, and coaches him to save people as a meet cute. Gero takes a commission to rescue the thief Kyoko Himekawa, who is famous for returning art to its rightful owners; during her latest heist, she was kidnapped. The rescue goes awry when Gero faces Water Master Ushio and a fierce fight ensues. |||||
| 2 | November 4, 2022 | 978-4-08-883323-1 | April 2, 2024 | 978-1-9747-4372-8 |
| "First One" (初めての相手, Hajimete no Aite)"Welcome Home" (おかえりなさい, Okaerinasai)"Operation Date: Commence" (デート開始シャチ♪, Dēto Kaishi Shachi ♪)"Guard Duty" (護衛任務, Goei Ninmu)"Sound Master" (音使い, Oto Tsukai) "Lord Chladni" (くらどに様, Kuradoni-sama)"Test of Courage" (肝試し, Kan Tameshi)"Gonna Make Some Fun Music Together" (ド楽しめそう, Do Tanoshime-sō)"Offering" (捧げ物, Sasagemono) Bonus Chapter 1 |||||
| After the mission, Gero and Himekawa go on a date; he relates a story from his childhood, as coached by Kinosaki, and after she reciprocates, he asks to start out as friends. For his next gig, Gero becomes "Daigo Oshima", a bodyguard for Shiori Ureshino, the designated heir to a family party supply company, at the request of her uncle. Ureshino has social anxiety, making an awkward introduction at a college party; she is targeted by Naruko, a Sound Master hitman hired by her aunt. After an attack in the classroom fails, Naruko's next attempt takes place during an off-campus camping trip where Gero shows off his cooking skills and Ureshino charms the other students with close-up magic. Local legends state "Lord Chladni" protected the village from disasters in exchange for child sacrifices; Gero saves Ureshino from a hallucination which would have had fatal consequences at the sacrificial shrine. Although Gero upsets Naruko's hallucinogenic stringed instrument, Naruko makes a realistic "Lord Chladni" giant, convincing the other students to sacrifice Ureshino. In the bonus chapter, Kinosaki explains they dress as a woman because the clothes are more fun, and they would be irresistible as a man. |||||
| 3 | February 3, 2023 | 978-4-08-883333-0 | July 2, 2024 | 978-1-9747-4612-5 |
| "The Weak" (弱き者, Yowakisha)"Bonfire" (キャンプファイヤー, Kyanpufaiyā)"Together With Me" (私と一緒に, Watashitoisshoni)"One More Thing..." (また･･･, Mata...)"The Bug Master's Wedding" (蟲使いの結婚式, Mushi Tsukai no Kekkonshiki)"Entertainment" (余興, Yokyō) "Sunset" (夕陽, Yūhi)"All The Happiness In The World" (100000000幸, 100000000 Sachi)"Hit Man Hunter" (殺し屋狩り, Koroshi Yakari)"The Meeting" (寄合, Yoriai) Bonus Chapters 2 & 3 |||||
| Naruko is defeated by Gero's poison trap and Ureshino uses illusions to dispel "Lord Chladni". She asks her aunt for her help to run the company and then invites Gero for a drink. Kinosaki and Gero attend the wedding of Bug Master Toshiki Hanamaki and Anna Kawakita, where they meet Needle Master Tsunagi and his three sons. During the ceremony, Gero fends off the Puppet Master's minion Yamada, who holds a grudge against Hanamaki, and the Bug Master explains how his branch family is subordinate to the Geros, one of the Five Great Families. After the wedding, Hamster Master Kimie Arashiyama hires Gero to protect her against the "Hit Man Hunter", who has killed the other masters in the Beast Clan. While Arashiyama introduces Gero to the Beast Clan, the Hunter takes Gero by surprise and stabs him. In the bonus chapters, Gero uses a toxin for more fun while Kinosaki sings karaoke, and he prepares a bento lunch for Himekawa. |||||
| 4 | April 4, 2023 | 978-4-08-883511-2 | October 1, 2024 | 978-1-9747-4904-1 |
| "Just A Normal Guy" (一般人, Ippanjin)"Three Days Left" (あと3日, Ato Mikka)"Ambush" (奇襲, Kishū)"Birdsball" (鳥類野球, Chōrui Yakyū)"Cross Sanguination" (混ぜ血, Maze Chi) "Cheap Tricks" (小細工, Kozaiku)"Together" (一緒に, Issho Ni)"Delicious" (美味いな, Umai na)"Amateur Work" (素人い仕事, Amai Shigoto) Bonus Chapters 4 & 5 |||||
| Gero is overwhelmed by Piichi, the Hit Man Hunter, but when Arashiyama leaps to Gero's defense, Piichi stops, saying they are different than the other Masters he had killed before. Piichi has targeted the Beast Clan (led by Toshiro Dogo, head of one of the Five Great Families); after Dogo activates Arashiyama's collar, it starts a three-day countdown to her doom. Approaching the Beast Clan's island, Arashiyama and Gero are split from Piichi and Kinosaki. After Gero defeats the Bird Master, Dogo challenges Gero and reveals his "cross sanguination" program to join strong bloodlines together; the Bird Master revives and adds the abilities of Spear Master Nagihiko Kushima, then collects a sample of Gero's blood before being defeated again. Meanwhile, Dogo's assistant Byakko collects a blood sample from Piichi. After resting and eating a meal prepared by Arashiyama, Gero defeats the Koala Master, but Dogo spirits Arashiyama away during the distraction and Gero is beaten by Dogo's innumerable goons until Water Master Ushio arrives to defend him. In the bonus chapters, Gero goes on a romantic fantasy date with Ureshino and Naruko reveals what is inside his unusually large backpack. |||||
| 5 | July 4, 2023 | 978-4-08-883581-5 | January 7, 2025 | 978-1-9747-5159-4 |
| "Water and Poison" (水と毒, Mizu to Doku)"Useless" (役立たず, Yakudatazu)"The Impure Master" (穢れ手, Kegarete)"All Fired Up" (やる気, Yaruki)"Honor" (誉れ, Homare) "Offerings" (供物, Kumotsu)"The Next Stage" (次の段階, Tsugi no Dankai)"A Happy, Ordinary Life" (フツーの幸せ, Futsū no Shiawase) Bonus Chapter 6 |||||
| Gero and Ushio combine their attacks to defeat the remaining Beast Clan members. Arashiyama has a flashback to her first encounter with Gero, when he rescued her from a failed mission, and calls together rats and hamsters to help her in the present. When Piichi and Kinosaki reach Dogo, Byakko delays them and he transforms her into his "frankenbeast" Hyakko, using a bloodline combining 93 Beast Clan branch families. Hyakko beats down Piichi until his spirits are revived by an unexpected call from his girlfriend and he prevails; while Piichi recovers from the fight, Gero and Ushio finally join the others at the hideout. However, Dogo powers up with Hyakko's blood and knocks out the two masters and Piichi; pushed to the limit and realizing that he needs other people to achieve his goal for a happy, ordinary life, Gero reaches a new level. In the bonus chapter, Tsunagi's fear that Gero has a weird wedding gift is allayed when Hanamaki opens it, revealing towels folded as flowers, on Kinosaki's recommendation. |||||
| 6 | September 4, 2023 | 978-4-08-883704-8 | April 1, 2025 | 978-1-9747-5230-0 |
| "TBD" (心髄, Shinzui)"TBD" (相棒獣, Pātonā)"TBD" (ゼロから･･･, Zero Kara...)"TBD" (センキュな, Senkyu na)"TBD" (もっと, Motto) "TBD" (愛の伝道師メイの恋愛相談会, Ai no Dendoushi Mei no Renai Soudankai)"TBD" (次分家の男段階, Bunke no Otoko)"TBD" (下呂家の将来, Gero-ka no Mirai)"TBD" (礎, Ishizue) Bonus Chapters 7–10 |||||
| Gero defeats Dogo with a refined poison which cannot be neutralized; in a last-ditch effort, Dogo attacks Kinosaki, but is paralyzed by Arashiyama, who rallies other Beast Clan branch families to control the beast partners in Dogo's blood. Byakko tries to escape with Dogo, but both are seized by a great wolf, the partner of Dogo's sister Tonako, who promises to punish them as the new head of the Beast Clan, then proposes marriage to Gero. During their victorious return, Piichi explains his strength comes from love and Arashiyama confesses she likes Gero but currently is not his equal, vowing to become stronger and win his heart; inspired by the women he has met, Gero also promises to work on himself. He struggles socially while Kinosaki dispenses love advice, but she says he is making steady progress. When Akari warns him about Teruaki Gero, a cousin who was engaged to her, Teruaki poisons the crowd around them and attacks Kinosaki while they visit their younger brother Okuto; during their fight, Teruaki begs Gero to kill him and concentrate on being the head of the Poison Clan, forgetting the distraction of marriage. In the bonus chapters, Himekawa flusters Gero with bikini photos, Ureshino bonds with him over the manga Ropes of Fate, Kinosaki hires Ushio for the fight against Dogo, and Piichi watches a movie with Marin. |||||
| 7 | December 4, 2023 | 978-4-08-883749-9 | June 3, 2025 | 978-1-9747-5605-6 |
| Chapters 52–61 |||||
| 8 | March 4, 2024 | 978-4-08-883873-1 | — | — |
| Chapters 62–71 |||||
| 9 | June 4, 2024 | 978-4-08-884036-9 | — | — |
| Chapters 72-81 Bonus chapter 11 |||||
| 10 | August 2, 2024 | 978-4-08-884156-4 | — | — |
| Chapters 82–91 |||||
| 11 | November 1, 2024 | 978-4-08-884302-5 | — | — |
| Chapters 92-100 Bonus chapters 12–14 |||||
| 12 | February 4, 2025 | 978-4-08-884434-3 | — | — |
| Chapters 101-110 Bonus chapter 15 |||||
| 13 | May 2, 2025 | 978-4-08-884544-9 | — | — |

### Chapters not yet in tankōbon format

These chapters have yet to be published in a tankōbon volume.
* Chapters 111–119
* Bonus chapters 16–18

## Reception

Marriagetoxin was nominated for the Next Manga Award in the Best Web Manga category in June 2022, and ranked eighth out of 50 nominees. It also ranked fifth in the Nationwide Publishers Recommended Comics of 2023. The series was recommended by Koyoharu Gotouge, Gege Akutami and Mogumo, the character designer for the anime series Mobile Suit Gundam: The Witch from Mercury.
The first volume received positive reviews for its art and action sequences. Hikaru Gero has been singled out as a "[v]ery relatable lead" with praise aimed at his design and his relationship with the "bubbly and energetic" Mei Kinosaki. Some criticism was aimed at Kinosaki's supporting role in the story rather than being a "fully realized character."
In Anime News Network's year-end retrospective, Lucas DeRuyter wrote that: "Marriagetoxin's attitude towards dating is so healthy, and it was considered a shoo-in for my pick for the best new manga of the year."