History Fanfic / DekiruTheFusionHero

** On top of that, it seems that people who fuse with Izuku adopt some of his personality traits and [[JustForPun quirks]] (But not the other way around). For example, Ochako and Momo started calling Katsuki "Kacchan" (much to the latter's utter annoyance) like Izuku does, [[spoiler:and Tsuyu started to develop a crush on Ochako]].

** On top of that, it seems that people who fuse with Izuku adopt some of his personality traits and [[JustForPun quirks]] (But not the other way around). For example, Ochako and Momo started calling Katsuki "Kacchan" (much to the latter's utter annoyance) like Izuku does.

** On top of that, it seems that people who fuse with Izuku adopt some of his personality traits and [[JustForPun quirks]] (But not the other way around). Ochako and Momo started calling Katsuki "Kacchan" (much to the latter's utter annoyance) like Izuku does, and Tsuyu started to develop a crush on Ochako.

** [[spoiler:Multi-person fusions are even worse than regular Human Fusion. While the fusions are more powerful, they drain even more stamina from all the component partners (especially Izuku) and can't be held together for long]].

* CoolBigSis: Satsuki worships the ground her older sister Tsuyu walks on. She's also very eager to see Tsuyu fused with Izuku.

** Katsuki, being Katsuki, has many, but a major one is [[BigBrotherInstinct disparaging Izuku's Quirk]]. For years Katsuki has been trying to convince Izuku about how great his Quirk is, and now that they're at U.A., he won't stand for anyone putting down his best friend when he's finally proved all his nay-sayers wrong. On a more minor note, he gets easily annoyed when anyone other than Izuku calls him "Kacchan".

* GoodThingYouCanHeal: Trapped in [[spoiler:Tsuzuru's]] adhesive that no-one can get out of, the Nomu proceeds to just rip off its trapped flesh and let its regeneration take care of it.

** Just like in canon, one of the top students of Class 1-A eats a big helping of HumblePie after losing the Heroes vs. Villains exercise. Though, in this case, it's not Katsuki ([[AdaptationalNiceGuy whose ego is much more manageable compared to canon]]), but instead Shoto, who is defeated by the fusion of Izuku and Momo. Shoto was even teamed with Tenya, like Katsuki was.

* DestructiveSavior: Zig-zagged. When prepping for the Aizawa's Quirk Assessment Test, Izuku tries thinking of something he can fuse with, and thinks of the walls of the building... only for him to realize that no, ripping chunks out of buildings is ''probably'' not the best first impression for a hero to make.

** Thanks to having Ochako and Katsuki as his sounding boards, Izuku's costume design is slightly different than in canon. In particular, the hood and mouth guard are absent due to them noticing he'd look like an All Might copycat, and most of the material is composed of woven metals. Visually, its described as being nigh-identical to his alpha costume in canon, simply without the mask and hood.

** [[spoiler: Nomu is ultimately defeated by damaging it enough that it's HealingFactor just can't keep up anymore, before All Might even ''arrives'']].

** Izuku' first costume is an accidental version of this. The silver areas are actually woven metal that he can fuse with, but when he designed it he failed to take into consideration exactly how much fabric would be left after he absorbed the metal. It still covers enough of him to not be indecent though.

** Izuchako (Ochako Uraraka): "Gravity Manipulation." A level of gravity control both on herself and objects around her much more powerful that Ochako's to the point of it being easy to confuse it for telekinesis. Nausea weakness is still present, but not as much as if it where Ochako alone.

* GodzillaThreshold: [[spoiler:During the USJ arc, Izuku initiates a second triple-fusion with Katsuki and Ochako, despite having only just learned he could do that ''on that day'' (and by accident, no less), to hold off Nomu until help arrives. He knows he's risking severe, potentially fatal, exhaustion in doing so, but the circumstances are so dire that it was the only option available if all of Class 1-A (including Aizawa and Thirteen) were to survive. In return, Katsuki and Ochako don't fight him on this despite being the most vocal opponents of his self-sacrificing tendencies, because as much as they hate it, they know he's right]].

* ExposedToTheElements: The result of Izuku absorbing his costume.

** Aizawa ''probably'' shouldn't have let the girl whose power is "Turns off gravity" go first in the ball throw test. They never get that ball back.

** Katsuki, being Katsuki, has many, but a major one is [[BigBrotherInstinct disparaging Izuku's Quirk]]. For years Katsuki has been trying to convince Izuku about how great his Quirk is, and now that they're at U.A., he won't stand for anyone putting down his best friend when he's finally proved all his nay-sayers wrong.

* CastFromStamina: It's implied that how long Izuku can stay in a fused state is based on stamina, as especially draining moves can eat through his [[HourOfPower transformation time]] faster than is normal. [[spoiler: Three-person fusions seem particularly bad about this, when Tsuzuru reverts back to Izuku, Minoru, and Tsuyu, the latter two are tired and sore, but it pales in comparison to Izuku's state, as he's ''literally steaming'' and covered in sweat and reddened skin, though he recovers quickly, and feels like he's just been training for ''hours'']].

** Just like in canon, one of the top students of Class 1-A eats a big helping of HumblePie after losing the Heroes vs. Villains exercise. Though, in this case, it's not Katsuki (whose ego is much more manageable compared to canon), but instead Shoto, who is defeated by the fusion of Izuku and Momo. Shoto was even teamed with Tenya, like Katsuki was.

* AdaptationalNiceGuy: Katsuki is much nicer in this fic, as a result of Izuku developing a Quirk when they were kids and others ''still'' bullying him for it, Katsuki became Izuku's OnlyFriend for a long time. While he can still be a {{jerkass}} in the present, he comes across more as a JerkWithAHeartOfGold to Izuku and, later, Ochako.

** Human Fusion is treated like this. While it isn't explicitly ''forbidden'', it's unpredictable nature means it's best used only as a last resort. Not to mention that prior to gaining some tips from Mandalay, he ran the risk of exposing All Might's secret due to its MentalFusion nature. [[spoiler:Notably, the first time Izuku starts spamming the technique in a short time-frame is during the USJ arc, which is an explicit life-or-death situation]].

** However, this also allows their components to involuntarily learn secrets and details about each other, such as All Might's secret. Izuku is currently taking tips from Mandalay about keeping thoughts separate, and it hasn't been made clear yet if Momo has retained any stray thoughts from the fusion.

* FusionDance: Obviously! Izuku's abilities takes direct inspiration from Kevin Levin's Osmosian abilities in WesternAnimation/Ben10, and the fusion properties of both Manga/DragonBall and WesternAnimation/StevenUniverse.

* AccidentalInnuendo: InUniverse example. As Izuku got older, Fusion started to mean something more perverted and laughable to his peers, which led to him getting mocked throughout middle school. Ochako made it a point to go straight to Izuku's house rather than tell her parents what happened during the Entrance Exams because she was afraid they'd get the wrong idea.

* AllYourPowersCombined: The unique Quirks wielded by Izuku's human fusions (referred to as "Quirk Mutations") are all variations of their parent-component's Quirks, making them more flexible and powerful. Such mutations include:

* HeroicSelfDeprecation: The mockery from his classmates for his Fusion Quirk has given Izuku a bit of a complex about it, and although he's gotten a bit better about it, he still has trouble seeing much value in it sometimes, as mentioned below.

* ChromeChampion: If enough metal is on hand, Izuku can fuse his entire body with it, turning him into this. Moku, Izuku's fusion with Momo Yaoyorozu, can do the same, but without the ElementalBaggage.

* GoodThingYouCanHeal: Trapped in [[spoiler: Tsuzuru's]] adhesive that no-one can get out of, the Nomu proceeds to just rip off its trapped flesh and let its regeneration take care of it.

* StoryBreakerPower: Even with DramaPreservingHandicap at play, Human Fusion edges dangerously close to this, especially now that Izuku has inherited One for All. With there being so many different heroes with unique Quirks that Izuku can fuse with when he finally goes pro, there is theoretically no limit to his power -- he can ''literally'' do anything.

** Aizawa ''probably'' shouldn't have let the girl whose power is "Turns off gravity" go first in the ball throw test. They never get that ball back.

*** He also didn't take into account whether or not the building would be able to ''withstand'' the weight from the ice he was creating, allowing his opponents to further destabilize it on purpose, and by freezing himself in the room with the bomb in it to guard it, he left himself blind to what was going on outside.