Refine the following crossover fanfic between High School DxD, Bakemonogatari and Fate/Stay Night: Kalied Liner Prisma Illya, with elements from Eromanga sensei and Majikoi: Love Me Seriously, pretending that DxD remained true to its origins as a ultra-fantasy, ultra urban fantasy light novel which started in 2008 at the height of edgy anime, manga and visual novel and the rise of moe, combining aspects of both and keeping in mind the Fate series combination of science fantasy, high fantasy and dark fantasy while making it as interesting, anime style and light novel style as possible as possible, retaining as much dialogue and exposition as possible:                                                                                
                                                                                                                                                    
 [Issei Hyoudou's Room]

[Hyoudou Family Mansion, Kuoh]

[Kyoto, Japanese Home Islands]

The brown-haired young man who was known to his classmates and schoolmates at Tenbi Gakuen [1] as the 'breast connoisseur' and 'sultan in training' due to his perverted declarations and tendency to hang around the most famous of the Perverted Trio, Matsuda and Motohama, let out a soft sigh as he shambled over to his large four poster bed and let himself fall on the satin sheet covered mattress with a plop, hands resting behind his head. A few moments later, the sounds of small feet rustling toward his direction could be heard and then, three young girls of middle school age entered the room, the last one making sure to close and lock the door behind her.

"Großer Bruder Kaito!" [2] The shout of worry was clearly high-class German, the language of the aristocrats and nobility of that great nation, but you could see a slight middle-class Japanese influence slowly slipping in, the first of the girls rushing to the young man's side and frantically examining him as if he was an injured solider returning from a battlefield. Her long, sliver-blonde hair shined with an unnatural hue as she dashed toward the teenage boy, a stark contrast to her now ruby-red eyes.

As in response to this act of concerned worry from a loving younger sister, a deep, rumbling voice echoed mockingly inside the young man's head.

Never in my countless millennia of existence, would I have ever thought of or expected something like this to happen. Truly boy, you are the most interesting host I have ever seen in a long time. Though I wonder why it took you so long to realize that the Einzbern girls and the Sakatsuki heiress [3] had such strong feelings for you...could it be because you're scared of what will happen if the Gremory woman, her peerage members and or the glasses-wearing bookworm that leads the student council ever find out about Illya-chan and Chloe-kun?"

He wisely choose to ignore this mocking commentary on his relationship skills and tried to instead focus on what he should say to the three girls who have risked everything to try and save him from himself on this clear spring night. Hopefully, Sagiri-chan wouldn't try and take his shirt off in her eagerness to play nursemaid and end up exposing the scars and bullet wounds that were peppered across his torso to the other two girls in the room with her, Nanaki-chan might act like she was preparing for an adolescent career as either a gyaru or female banchou and the ever stoic Miyu reminded the only boy in the Hyoudou family of the combat gynoids in those sci fi anime, manga and movies he liked watching as a young boy, but his younger half-sisters and the Edelfelt ward were still in middle school, Gods damn it!

The circumstances under which he had received those marks was something that he was not ready to reveal yet, not even to Lizel-chan...

Though I have to admit...Sagiri-chan has really grown into a beautiful young lady...tehehehe. No Yamato, what the hell were you thinking there man? She's your younger half-sister...for crying out loud! Sure, she and Kuro-chan might look pretty cute in those cosplay uniforms of these...but...

He didn't get to finish that thought as a pair of soft lips were placed on his and a small tongue entered his mouth, causing him to moan in surprise as the silver-blonde loli's slender frame was pressed against his body. The young man, surprised by this turn of events, tried to push her off him but this only caused her to intensify her efforts. When it was finally over, both Sagiri and Kaito's faces were the hue of a tomato, although Sagiri seemed more embarrassed by the whole affair.

"J..just what the hell was that...I...Illya-chan?!" Kaito stuttered suddenly, still refusing to believe what had happened. A sudden slap on the left cheek caused him to quickly snap back to reality. Rubbing his sore face he quickly turned his head towards the other girls, only to see Chloe/Nanami/'Kuro' shaking her head and Miyu on the verge of tears.

"Y..you really don't have a clue, d..do you onii-chan?" Suddenly the wand that was in Illya/Sagiri's hand glowed and the pink dress that she was wearing transformed into a rather transparent negligee outfit that wouldn't be out of place during a seduction...or a wife trying to attract her husband during a honeymoon."I...I thought K..karen nee-chan was r...really joking when she stated that you could be rather dense at times, b..but it turns out she wasn't wrong at all..."

Poor Issei could only mumble out in shock, "No way...that can't be right...am I having one of those weird dreams again? I know that my little sisters like me a little too much...but for them to love me this deeply...then that means.."

He wouldn't get time to finish, as Kuro and Miyu both jumped on the bed and started to make out with him as well, causing the reclusive young man to blush even further. Illya had been pretty aggressive during their snogging session...but since she and the other girls were still kids, it was obvious she was still inexperienced at affairs of love. Neither Chloe nor Miyu seemed to have that problem this time around, although the Edelfelt maid seemed to be a bit mechanical when going about the task and Illya's twin sister [7] seemed like she was literally going by the book of seduction.

When the three of them finally separated from each other, Miyu's cheeks were completely scarlet as the normally emotionless girl tried to make herself seem invisible after that rather intimate moment. Chloe on the other hand seemed a bit bored but otherwise happy. "Yum, yum. Onii-chan's mana is so tasty and delicious, and the best part is...he has so much of it!" the petite pinkette shouted in excitement, causing Illya's face to flush red again.

The silver-haired girl pouted once more. "You didn't have to say that part out so loudly Chloe! Geez, you and Issei really did pick up a lot of your perverted antics from Dad...hmph" She did a rather poor imitation of a disgusted noble lady and quickly turned away, her small face still as scarlet as ever.

Meanwhile, Issei was scratching his forehead as he tried to understand what was going on. His cute, beloved, little twin half-sisters whom he loved very much in the world, had decided to act on their obviously deep feelings for him after he had caught them sneaking out of bed to fight monsters who apparently transformed into playing cards when killed, and to make things even more confusing had brought their rather shy best friend and partner in monster hunting into this not-so-secret love confession.

The words stumbled out of his mouth before the brown-haired faux pervert could even stop himself.

"So, the reason why you girls have been so sleepy and rather cranky these days, is due to the fact that you've basically been going on dungeon raiding in order to collect these "Class Cards" when you're supposed to be getting a good night's rest?"

Illya tried to keep her cute face turned away as her cheeks got even redder, while Chloe/Kuro/Nanami's grin widened at the fact their beloved big brother wasn't such an idiot after all.

Miyu however, still tried to remain professional even though you could see a small spotch of red on her cheeks. "You're absolutely right Issei-kun, although dungeon raiding wouldn't exactly be the correct term for what we do. Though we've been fighting a lot of the monsters lately, so please forgive us if we've been a tad sleepy these days," She put a hand over her cute mouth to cover her yawning.

Chloe, ever the bombastic and expressive one out of the Einzbern twins, helped finish the statement. "But I have to admit, this whole thing has been very fun! A lot more interesting than sitting in class learning boring lessons all day...I wonder if we could jump a few grades so that we could finally be with our one and only beloved...though I have the feeling we'd have to share him with more than just Miyu-chan..." The pink-haired short stack pouted somewhat at this prospect.

A perverted grin appeared on Issei's face as he finally managed to work out the reason for the rather strange set of dreams he'd been having for quite a good while now. " So that explains why Illya and Nanaki-chan have been sneaking into my room and giving me a make-out session when they think I'm sleeping...you two need to recharge your magical energy after battle. Correct me if I'm wrong,"

Now it was Kuro's turn to blush and hide her face away in shame. "Huh!? How'd you know about that, Issei!? And don't call me Nanaki-chan!"

The apprentice of Luviagelita Edelfelt was rather hopeful when she heard those words, muttering the words, "He knows, he knows, HE KNOWS!" under her breath in hopeful excitement.

The brown-haired youth kept his perverted grin as he eyed his younger twin sisters and their best friend, noting how red their faces were at this point.

"I might be a diehard otaku and a loner with a weakness for oppai, but I'm not dumb, you know. I know you three have some rather strong feelings for me, which is why you choose to do the mana transfer ritual because both Illya and Nanaki-chan love me more than a brother.."

Chloe tried to turn her face away even further, the red on her cheeks providing a stark contrast to her dark mocha complexion. "It's not like I like him or anything...but he isn't wrong there..."

Realizing that she had an opening, Miyu quickly struck. "That's just an act, right?" Of course, the black-haired girl knew that Kuro loved Issei as much as her and Illya/Sagiri, she just wanted to get back at the pinkette for all the times the latter had teased her while they were out hunting monsters.

Chloe's face turned even redder at this.

"I..I'd rather get my mana from onii-chan than Illya..."

Miyu frowned. "But we're meant to be a team..."

Kuro quickly retaliated. "But we can still be a team and be in love with onii-chan, right Issei?"

The two girls blushed even more at this as they leaned closer to each other, trying to appear seductive.

Said brown-haired boy, however, was blushing himself but pleasantly surprised at what he had just heard.

" O...of course. I'd be happy to accept the love of you three...but you know you have to wait until you leave high school for anything heavier than petting and kissing, right?"

Kuro's usual grin appeared on her face as she embraced her older brother in a bone-crushing hug. "That's fine by me!" the dark-skinned girl yelped, leaving a big, messy smooch on Issei's cheek. "Just remember to include Miyu-chan when you finally go all the way with me and Illya-chan,"

Miyu turned her face away again. "Y...you're joking, right?"

Issei's curiosity was piqued at this. "Before we start, I need to know something. That blonde girl who comes to pick you up when you come to visit us...Luvia I think her name was, she and Karen-chan [8] have feelings for me also, right? Because I've seen her blushing and looking away when she sees me, and I've heard her and Karen-chan arguing over who should marry me first."

The fact that Chloe and Illya's normally dense older brother had even asked this question stunned the normally stoic Sakatsuki heiress, but that wasn't the real shocker for her. What really surprised Miyu was how calm Issei was about the whole matter, it was if he had dealt with this whole thing before.

Kuro and Miyu both looked at each other and blushed even more.

"Y...you're asking us to j...join your harem onii-chan...I didn't expect someone as dense as you to pick up on that..."

Miyu's eyes widened at this. "S..so you knew? All along?"

Kuro wagged a finger. "Of course I knew! And Sagiri-chan knew as well, but she was in denial! Why do you think our magical girl outfits are even so lecherous in the first place? Hello~The Kaidelosticks are literally designed to act on the wishes of their chosen users!"

Sagiri, who had been silent for most of the discussion, finally found her voice and decided to share her opinion.

"So you basically want us, Luvia-teme and Karen-baka to be onii-chan's wives, right? But Kuro-chan and I are his younger half-sisters and Karen and Tsukihi are his full little sisters! Wouldn't that be incest?" Illya's completely red cheeks provided a stark contrast to her long silver hair and pale skin as she tried to hide her developing body from the prying eyes of both Chloe/"Kuro" and Issei.

Kuro's grin returned as she glared at her older twin. "I mean...this wouldn't be the first time our family tree has gotten messy. Plus, it should be pretty clear to you by now, that the flame brains love Issei-kun as much as we do, if not more! Sharing him as our husband allows all of us to express how much we love him, while preventing any unnecessary conflict from breaking out,"

Miyu, ever the walking encyclopedia, decided to add her few cents. "You do remember that the Einzbern family is infamous for its use of homunculi, right? I don't know why Karen-baka never told you this Illya-chan, but you were literally born as the perfect human specimen, most likely as a container for a grail replica like I was. Chloe seems to have gotten a bit more from your father, even though she is still an Einzbern by blood of course. And there's the issue of Tsukihi-chan...[9]"

The black-haired Japanese beauty scratched her chin as she tried to figure out what to say in this rather confusing situation.

"Although she and Karen-chan were born to Miki-san and thus are Issei-kun's full little sisters by birth, the rather sad story of Tsukihi's inheritance of the leadership of the Matou clan throws a monkey wrench in the whole affair. The sad sack of worms responsible for Sakura-san's kidnapping not only implanted the family crest of his clan inside the poor girl, but did a blood adoption before that to ensure that his chosen victim would carry on his legacy, regardless of whether she wanted it or not.

That means that the children you four are eventually going to have with Issei-kun would not be affected by the effects of inbreeding, as the bodies of a Magnus and a normal human are so different they might as well be different species,"

The two youngest Einzbern sisters once again turned scarlet at the thought of having their beloved older brother's babies. "C..children...w...with I..issei-kun..." Sagiri was on the verge of fainting from the very thought of such a thing happening, not that the silver-haired princess would admit it out loud of course. She already had too much on her plate due to her double life as the infamous "Ero-manga-sensei", not that anyone else knew about that part of her life of course.

Her younger twin on the other hand, had no such compulsions and was happily singing a ditty about her future married life with their older brother, in German of course. After the dark-skinned girl had finished expressing her musical talent, she turned to Miyu with her trademark smirk before groping the black-haired girl, causing Illya to turn red and turn her cute face away again.

Meanwhile, Issei was just lying on his bed, trying to take in everything he had just seen and heard while not saying a word. Then his sharp mind quickly rebounded to Miyu's little speech and he quickly sat up, amber eyes wide.

"Homunculuni? You mean like Full Metal Alchemist which all the conspiracy weirdoes claim was a documentary on the Third Reich disguised as a popular manga and anime series? [5] You girls can't be serious...right?"

To his surprise, Kuro's expression softened into a small smile while she stretched out her hand to do a thumbs-up pose. "Yup, right on the money there, onii-chan. Though I really hate the fact that they portrayed our great-grandparents as lowly peasants and made Alicia-chan a boy...plus our hair is a beautiful silver, not a dirty blonde!"

Miyu nodded, fidgeting with the straps of her rather revealing outfit as she and Kuro prepared to kiss Hyoudou again. "You're right this time, for once. Though I wonder why Arakawa-san neglected to mention why "Bradley" ignored the offers of a united alliance against Soviet communism and Allied colonialism offered to him by the Japanese social democrats, in order to curry favor with the very same empire that had starved his people to death. I guess it was due to the fact that she wanted to write an entertaining story, and the boring details of espionage and politics would have proved a distraction from the already juicy story of alchemy and government conspiracies involving magic,"

Kuro quickly snapped back. "Hey!"

Miyu ignored this retort in favor of scooting closer to Issei on the bed, and pressing her young body against his muscular frame. "So, are you ready for a harem, Issei-sempai?"

Before Issei could even answer this question, the door flew off its hinges and a steaming mad Rias Gremory stormed into the rather sizable room, accompanied by a worried-looking Akeno and a red-faced Koneko who was trying to hide behind her angry, but obviously concerned mistress.

"ISSEI! Where are you...is everything okay?" The Empress of Annihilation's now blazing crimson eyes turned to the sight of Kuro and Miyu cuddling up with Issei in preparation to kiss him again. The scarlet-haired woman nearly had a heart attack from what she had just witnessed.

"D..don't tell me t...that y...you were r..running away from our h...honeymoon...j...just so that you could go sleep w...with t...those CHILDREN!"

Rias' bright scarlet hair was whipping furiously from side to side, as an immense pressure immediately fell upon the other people in the room,

Unfortunately for the brown-haired Hyoudou, the loud and proudly bold Chloe choose the worst possible time to open her mouth.

"And just who might you be, Cow-tits-sama? I'm sorry if we interrupted your precious wedding after-party, but onii-chan's been quite distant from us lately and we just wanted to have some family time for ourselves, isn't that right Illya-nee?"

The silver-haired girl squeaked in surprise when her bolder twin spoke up, but she quickly turned to the smoldering teacher that was currently cracking her dainty fingers and quickly nodded, becoming even more embarrassed at the Gremory heiress' judging gaze. "T..that's right, Himekami-sensei. D..due to all those extra lessons Issei-kun's been taking with you, he's gotten distant from us, and we were starting to get rather concerned about him. But now that you've announced your presence so forcefully...it seems that onii-chan's been hiding quite a few secrets himself,"

Things were only made worse when a rather short girl with short violet hair done into a bowl cut, wearing a rather exquisite kimono with a floral pattern design pushed her way through the small crowd that had gathered in Issei's room, only to frown slightly when she saw Chloe and Illya clinging on to Issei.

"Well, it seems like the two princesses and that robot servant of the Edelfelt girl got to Issei-nii first. What a shame. And I was hoping to have him all to myself before the other girls could find him...ah, well. This was always going to happen anyways, no matter what Issei or any of us did,"

Kiba and Akeno, who due to their enhanced senses had overheard everything that was just said, both sweatdropped, with Kiba's blue eyes widening at the name "Edelfelt" and Akeno grinning evilly when she realized exactly what was going on.

The surprise didn't end there, as the sound of rushing footsteps and then, labored panting caused the Gremory peerage and their mystery companion to quickly whirl around. The purple-haired girl's mouth dropped open and Rias narrowed her eyes at the presence of more unwanted intruders.

"T..tsu-chan? W...what are you doing in onii-chan's room...and who is that strange gaijin oba-san who seems to be quite unhappy at our presence. My, my. I knew our brother was strange and probably had a large harem of girls that he had kept hidden away from us, but I'd never expect him to have such exquisite tastes. A high ranking member of the 72 Pillars of the Underworld, with a smoking hot body to boot? No wonder Issei-kun had so many extra lessons when regular school ended. What do you think, Luvi-baka?"

"Hmph. I'll concede this point to you, Karen, but don't think you've won just yet! We still need to find Illya and Miyu and..."

The Gremory heiress' shocked expression put an end to the bickering spat. "L...luvia-c..chan?" The scarlet-haired MLIF couldn't believe what she was seeing. Rias knew that her beloved Issei-kun dreamed of becoming the Harem King and as thus, would have a lot of other women, but for even her one-time friend and rival from Germany to be involved...

"T...that idiot Lizel...you have feelings for Issei-kun, too? And he's your fiancee?"

The normally calm and reserved 'Koneko', her deep feelings for Issei clouding her normally stellar judgement, decided to try and express her opinion on the rather confusing matter. "So Hyoudou-s...Issei-kun, far from being the only child of a stereotypical middle-class family contrary to what the other teachers and the rest of the student population at our school thought, was in fact the 'normal' older brother of both the Tohsaka and Matou heiresses...and not just them, the supposedly non-existent 'Duo Einzelbernd' [4] as well, if my growing suspicions about the two girls cuddling up with him on the bed are correct as well,"

Unfortunately for Issei, Rias' sharp ears had heard everything, and even though she was glad that her favorite student's supposed dream of becoming the "Harem King" wasn't just cheap talk, she was still mad that the brown-haired boy had tried to keep the truth about his family hidden from her for so long.

"You know Issei-kun, I am somewhat relieved at the fact that your ambitions of becoming this so-called "Harem King" are in fact real, and not just delusions created by the hormonal mind of an adolescent male. And I have to say, I didn't expect you to become so bold in claiming your conquests. But still, there is something very concerning that has come to my attention, and I believe that it needs to be addressed before we deal with anything else,"

The redheaded teacher's stern gaze would have been enough to send a weaker man to his knees, but Issei was no idiot despite his pretense to the contrary at school. Swallowing his pride, he sat up straight and faced his King and mistress, keeping a serious face as he did so.

"Why didn't you tell me, or the other members of the ORC the truth about your family? When I brought you back from the brink of death using my evil pieces, I was under the impression that you were just an average joe with nothing special about either him or his family tree, based on the way you and your parents acted. And you didn't do anything to correct that impression as the months went by either. So speak up now and be as honest as possible, and make sure to leave nothing out. I want the full truth, no matter how painful and inconvenient it may be,"

Issei gulped, before nodding and retelling the story of his family starting from the time his mom and dad discovered an unconscious silver-haired girl [Illya's mother, Irisivel] in the forest while on a business trip in Germany many years ago, when Issei was just a young boy[6]. This was going to be a long night...