You tracked De-kun down after school the next day; he was busy having a quiet conversation with blo - Bakugo. Still getting used to that. Anyway, Bakugo stalked out without prompting once he noticed your presence, so you didn't have to escalate the situation, much to your disappointment - you still wanted his 'save data' after all.
De-kun watched Bakugo leave with mixed expressions of relief and concern, before turning to thank you quietly.
"So, what do you want to test out today, De-kun?"
He brightened at the mention of committing crimes against nature, and began rummaging through his bag.
"Oh - right! You know how you mentioned your 'save data'? Well, something about it seemed familiar, so I spent a couple of hours last night going through the advanced biology textbook…"
"And? What did you find?"
"Absolutely nothing!"
"...huh?"
"There was nothing in the advanced book, so I went back to the basic one, and on one of the very first pages -"
He finally found what he was looking for, and flashed the page at you:
"Stem cells! One of the very first things we covered in class. They're plurip-"
You tuned him out as you started mentally strangling yourself for not realising this sooner. How?! You've had what, eight years? The internal screaming continued.
"-rejected by the host body; that's why you wound up in hospital the first time."
He beamed up at you as you slowly placed your hands on his shoulders, a grin affixed to your face.
"De-kun, thank you so much for this, but Kaede needs to go beat their head against a wall right now."
Slightly confused, Izuku stopped you before you could leave;
"But… what about the other things I was planning on testing?"
"...Other things?"
He swapped his textbook for a notebook, flicking through it to display several pages of preprepared results tables.
"I had a couple of experiments planned to help narrow down what your quirk actually is. I figured if we worked that out first, it would make testing your capabilities easier."
You stared in surprise at the sheer amount of thought he'd put into this. Which was, apparently, the wrong thing to do, as your companion immediately began to panic.
"S-sorry! Was this too much?! I'm so sorry I just get really excited about this sort of thing and I didn't think about how weird this would seem to you and I'm sorry just please don't let them e-"
You cut him off by patting him on the head, still too shocked to formulate more than a few sentence fragments.
"Stop apologising. Let's go - your house."
A few minutes passed by in awkward silence as the two of you walked, De-kun occasionally glancing over at you with the look of a startled rabbit. Damn rabbits, always too fast for you to catch - Watership Down made it look misleadingly easy.
Anyway, you needed to check something:
"De-kun, you're not a conspiracy theorist, are you?"
"..No?"
Well, that rules that out. Hmm.
"Cultist?"
"No. Where are you going with this?"
"So... you're just a regular person, who just so happens to actually want to help me, to no benefit to yourself?"
"I-is there something wrong with that?"
Oh, wow. How was it possible for someone to be this nice? Even after you'd made him go through that… event, which, as your mom had explained, may possibly have been a tiny bit scary for someone who didn't know that you'd be fine with most of your internal organs vaporised. People this nice were an endangered species, according to her, and on your pride as a hero, you were not about to let such a rare specimen get damaged.
"...Never change, De-kun."
Although he didn't know it, the little deku scrub had just gained a new guard-catlizard.
---
An hour and two bags of sugar later, De-kun's mom returned from work. She then attempted to drown you with her tears. Apparently, her son hadn't brought anyone back with him for years, which was evidently a bad thing. Maybe context mattered? Did that mean your parents would be happy if you brought people to your house and didn't try to eat them? Then again, they'd probably be fine if you just brought home some humans instead.
Inko eventually paused her murder attempt, and your conversation turned to heroes; favourites, ideal names for yourself, what you'd do. It was a very one sided conversation, as you both univocally agreed on All Might, had none, and didn't know, respectively. So, the conversation again turned to Izuku, which appeared to be her nickname for her son.
Speaking of whom, De-kun was certainly taking a while to get that book; you wondered what was keeping him.
---
Izuku was in fact outside the living room, his back pressed against the door, and was currently wondering why he had ever thought bringing you to his home was a good idea. This was, if he remembered correctly, the sort of thing people did with stage two friends at minimum, not acquaintances that they weren't even sure weren't planning on feeding them to their 'friends'! He dragged his hands down his face in frustration. He'd been so caught up in the thrill of theorising what their quirk could be that he'd forgotten how dangerous it was to let people get so close.
...
...At least Mom was happier than he'd seen her in a while; she was always so concerned for him, even before he'd started worrying her by letting her see how much the loss of Kacchan's friendship had affected him.
The sounds of excited chatter, interspersed with laughter, echoed throughout the darkened hallway.
...
He sighed; maybe he was just overthinking this. He tended to do that a lot. What was the worst that could happen, anyway? …Okay, that was maybe not the best train of thought. He did not need such graphic mental images.
But really, maybe he was just being paranoid? Judging by what he saw on tv, it's not like his experiences with Kacchan could be considered a normal friendship, so why not give it a shot and deal with the inevitable backfire later?
...they sounded like they were having fun in there.
...
He straightened, turning to face the door in a surge of determination. Kacch - Bakugo was not going to ruin this chance for him. Who cares if they would find him pathetic? Was he going to apologise for having dreams? He'd promised himself that he wouldn't let other people's opinions get to him any more - and heroes don't lie to people.
Clutching the notebook tightly against his chest, Izuku stepped into the living room.
---
The first year of your friendship was very productive, thanks to Izuku: the two of you had narrowed down the specifics of your quirk to some kind of self-biokinesis at a cellular level, minimum, as well as a secondary quirk of awareness of live, eaten animals. All within the first week.
He helped make his first crime against nature within the following month, when he had you attempt to change something inside you in a similar way to how you could edit your own body; a nest of huntsman spiders he'd found had been used as test subjects, as there was no way you were going to risk any of your friends. While you found that you couldn't [focus], or directly change the creatures to the same extent as your own body, you could give the decomposition effect a target, as well as [push] certain cells into your victims. In this case, the target was the spider's [potential], which was highlighted by your quirk in rainbow neon. While it took some practice to hit the correct area of their cells, resulting in some horrific failures that repulsed even you, you eventually managed to replace the 'instructions' for the spiders' relatively harmless venom with that of your friends'.
And so, Izuku accidentally unleashed an army of giant spiders with agonisingly painful venom into the world, after forgetting to tell you that you weren't supposed to release them once you were done. You were so proud when the public health warnings started appearing on the news.
---
However, the most important breakthrough came during the summer holidays. Due to the fact that every organism you disconnected from yourself always died, you couldn't save time by creating and editing them bit by bit, so the two of you had waited until there was more free time to test this aspect of your quirk.
"So what exactly is the problem with them?"
Izuku prodded the dead centipede - less resource-intensive to make than a cat.
"There's just something missing from them; there's nothing wrong with their components, but they just don't work on their own once I disconnect them…"
You picked up the useless thing and gave it to Ankheg, the least picky of your girls. Silence descended as he thought, occasionally glancing over to the spread of open textbooks, strewn across your bedroom floor. After a while, he picked one up, flicking through it as he spoke.
"You mentioned… when you create these organisms, you don't have to 'push' energy into them?"
"No, it just happens naturally as I grow them."
"And…" he paused, and went back a few pages "you checked that the heart, nervous system, all that, work before disconnecting?"
"Yes. Of co -"
He slammed the book down, scanning the page, and you grinned - you knew that look in his eye. He'd found something.
"Kaede, have you tried putting more than the required amount of energy into them, just before you disconnect?"
You didn't answer, already in the process of creating another - energy… where would that be? You [pulled] on that intangible sense of 'you', a strange sensation that left you tasting spots in your inwards sense, and [pushed] it in the direction of the centipede-shaped growth on your side. You couldn't truly isolate the 'you-ness' and the route it took inside you tore, heated, feeling 'not'.
You kept the transfer going as you disconnected, only a split second, but it left you feeling more exhausted than all of the days previous attempts at creating life combined. The new centipede dropped onto the floor, and you sagged to the side, numb. Still watching.
It twitched.
You slowly reached over and poked an antenna.
It began tearing into your finger.
"YES! OhmygodyesFINALLY!!"
"Gah! Kaede - can't - breathe…"
You let him out from the bear hug and tried to do a backflip. Tried. Your mind was racing, filling with possibilities for the next step. Birds: need a bird, see how hot air balloons work, maybe planes maybe buy one EAT IT flying.
Izuku just sat there, sharing your joy. And now there was guilt - shooting through you, a sobering emotion that burst your giddiness. He's helped you so much… for nothing. It was uncomfortable. It wasn't fair. You picked yourself up from your position on the floor, and faced him.
"Izuku, thank you. This is more than enough, let me help you now."
"W-what?! No, no, really, it's fine. You don't need to do anything for me."
The look you had on your face caused Izuku to pale; it was the same expression you'd had when you'd come up with the brilliant idea of making spiders 'bigger, and with like, acid or something'.
"We're going to UA, De-kun. Who's going to stop us preparing ahead of schedule? Now… let's see what sort of upgrades we can give you."
Main Action:
[ ]Kindly inform his metabolism that it isn't the Stone Age - you can stop hoarding that fat now. Get some muscles instead.
[ ]Put in a request for some subdermal armor - De-kun's too squishy as it is.
[ ]De-kun could do with a few more friends in his life, don't you think?
Additional Actions: Write-in.
---
AN: Last major timeskip DONE. Onwards - to the plot derailment!!
I'm only offering minor changes to Izuku for now; he still has those pain receptors after all, and MC doesn't want to hurt him.
It didn't fit in because of the pacing, but the reason that they kept dying because the cats/centipedes weren't functioning on their own, because instead you were controlling them manually, which didn't carry over when you disconnected. It's like you were checking to see if a generator was switched on, only when you checked the indicator light, you already had a light pointed at it. If that makes sense. Can't get too detailed, there's still a few things I'm going to leave for you to work out about how the specifics of the quirk works.