Now, it may be some time before the full fic of this gets published, if it does at all. I saw a few problems with the story as I was writing it, with not enough of the Spark being used. The first two chapters are fine, and the third chapter is mostly fine, but it needs work from then on. Plus, I can only get the first volume of the manga from the library, so progress will be slow, even once I get either further volumes, or the anime on Blu-Ray (they only have the Blu-Ray over here).

That being said, writing this Girl Genius crossover has inspired me to do a similar one in the world of Naruto. Look for Genius, Madboy, Fox in The Forbidden ANBU Files.

MAD SCIENTISTS CAN BE HEROES TOO!

CHAPTER 2:

ONE FOR ALL

Izuku gaped at his idol. "…What?" he asked, a surprisingly intelligent response, given the shock he was in.

All Might sighed quietly. "Kid…I'm gonna take a risk with you. But I saw the conviction in your eyes. I think you might be worthy of inheriting my power. A Spark is dangerous, true, but I've seen them create some of the best and greatest tech the world has. Any hero is dangerous. I'm offering you a chance to inherit my power."

"Your power?" Izuku asked. He knew that All Might was rather coy about his Quirk, avoiding answering journalists about where it came from. Certainly, there was endless speculation on the internet about its true nature.

"Yes. It was passed down to me, like the Olympic Torch. And now, it may be your turn. The power of my Quirk…combined with the Spark…it frightens me, frankly. But I've been searching for a successor for a while. My power is called 'One for All'."

"One for All?" Izuku asked.

"Yeah. The first person to have the power cultivated it, and then passed it on. The second refined that power, grew it, and then passed it on. Again and again, until…well, you've seen my power. Those who cry out for salvation, and those with the valour and fidelity link to form a network of power. You may be a fanboy, and the Spark is dangerous, but even when a boy who was a bully was in trouble, you only took enough time to get a weapon out of your bag, one which you made sure wasn't lethal, and headed over, even if you might be killed. You were more heroic than anyone else nearby. Of course, it's wholly up to you."

After a moment, Izuku gave a rather sad smile. "…You know, until I unlocked the Spark, I would have given anything for such power. I wanted to go into UA on my own merits, though, even when I unlocked the Spark."

"Oh, trust me, kid, you have to earn One for All. This power needs training to use, don't you worry. It comes with catches."

"Hey, I'm not rejecting it. I accept. Not because I need this power or want it…but because you want to pass it on to me. Because few people have told me such kind words before. You trusted me with your secret. I don't want to let you down."

All Might chuckled. "You accepted pretty quickly. A little slower than I thought, but…hey. The power of One for All…and the power of the Spark. Brawn, and brains. Okay, kid. Meet me in two days' time at 6 in the morning at the Takoba Municipal Beach Park. We start the training early."

While Izuku didn't tell his mother everything about what happened, he did tell her some of the more pertinent things. Nothing about All Might's power or his transformation, only that All Might intended to tutor him. She had seen part of what had happened on the news, and had berated him for his recklessness, but at the same time, had praised his desire to help Katsuki, despite the other boy's belligerence. She knew that going to UA was a lifelong dream of her son's, and was glad he was about to make it a reality.

Izuku got to Takoba Beach about half an hour beforehand, and spent part of the time disassembling some of the junk, particularly the stuff that had caught his eye. About fifteen minutes before the appointed time, All Might turned up, albeit at first in his skeletal form. "You're here early," he remarked.

"I've been here before," Izuku said. "While it's a shame people use this place to dump their rubbish, there's a lot of useful stuff amongst the junk. It's a boon for a Spark looking for spare parts. I guess I also help clean it up anyway by taking a few things home. Mum doesn't like me bringing too much junk home, so I have to keep it out of the way, though. But every bit I take home is less cluttering up here, and anything I don't need, I throw in the rubbish, or else take to the dump myself."

All Might smiled, changing into his muscular form as he did so. "Good thinking!" he said with a thumbs-up. "In truth, most young heroes are in it for the fame and glory. Think of this as volunteer work. It may be unglamorous, but it's still fine work! Now, let's put it to you bluntly: you're not a worthy vessel for One for All. And when I say 'unworthy', I don't mean psychologically. It's your body."

Izuku, stung at first by the appellation of 'unworthy', thought about it. "Because One for All combines the strength of multiple people into a single vessel, so if I used it as I am now…it could kill me, or at least seriously injure me."

"Good! You got the picture! I'm going to be putting you through the paces, kid. This is going to be tough. UA's curriculum is the toughest, and not just physically, but also academically! While a Quirkless person may not be able to get in, a Spark would, but even then, they would face tough challenges. You have ten months to do this. That's why I've worked out a plan for you." He pulled out a sheaf of papers, and slapped it. "I call it 'Pass the Test, American Dream Style Plan'. Frankly, kid, it's going to be tough as anything. There's no shortcuts. Even if your Spark can, say, make some pretty good exercise machine or something, I still think you'll be barely ready in time for UA's entrance exam. And it's not like you can overdo it: try too hard, and you'll only end up ruining your body."

Izuku nodded. He'd need time for his body to rest between boosting his muscles. Maybe he could find a way around that. He didn't want to look like a musclebound hulk, but maybe there was a way of compacting muscles, or something that could help muscle recovery. Something to look into while doing this. "I've also got some training robots I made, like the drone I showed you. I'm pretty quick on my feet, and I've got decent stamina, it's really my strength that needs boosting. Hopefully, I'll get all of those up. Need to keep my classwork up. I'm not worried about the sciences or maths, it's languages, PE, social education, and so on I'm worried about. I mean, I'm good with those, but science and maths come naturally to me. I guess it comes with being a Spark."

"I've taken those into account, kid. I've even got a meal plan for you to ask your mother to follow."

"Good. I told her you were training me. And no, I didn't tell her that you were giving me your Quirk, or your predicament."

"Good. This is going to be Hell, I won't make any bones about that, Midoriya. But this is a crucible that will forge you into a worthy vessel indeed…"

All Might wasn't exaggerating. It was indeed ten months of Hell. But along the way, Izuku managed to figure out some ways to make his training easier, even accelerate it.

One of the things he had been working on was a 'sleep compressor', a device that basically sped up the process of sleeping to rest the body, at least mentally. Knowing that he would have even less time to rest during this period, he had even greater incentive to finally finish it, so that, while he was resting his body physically, he could use that time to study for his schoolwork. A month in, he finished it, and it certainly helped.

He could have considered either nanomachines or experimental drugs to help speed his muscle recovery process, but the former was still a bit out of his league, while the latter…well, he didn't want to have to deal with side effects during this critical time. He did consider a number of methods, though.

He did design a device that would stimulate his muscles gently while he slept, though. Not enough to be considered even a workout or exercise, but it would be enough to help get them to gain strength, even if by increments. They even made sure they wouldn't cause any problems by overtaxing his muscles.

Another thing he decided to do, when he had spare time, was a form of meditation. Not quite actual meditation, clearing one's mind, but rather, trying to become more aware of his body. During his training sessions with All Might, he passed the time mentally by asking All Might how, mentally speaking, he tapped into One for All. All Might's anecdotes and explanations helped, and Izuku knew that, if he could just control enough of One for All, he could actually use it without as much risk of injuring his body.

In a way, having the Spark helped. Even when the Spark wasn't actually active, it did confer a kind of hyperawareness at all times. All one needed to do was transfer it to one's body, and maybe it could help.

He considered creating some sort of powered armour: that was what he was intending to do to help him get into UA. Or else create cybernetic limbs. But he realised both might conflict with One for All. He might end up being too strong for the powered armour to cope with, and he could break the cybernetic limbs.

All through it, he bore the scorn of his classmates, especially Katsuki, who had gotten worse, with the verbal abuse at least, since Izuku had rescued him. Izuku strove, with considerable difficulty, to ignore him.

One thing All Might DID ban was Izuku turning any of the junk into machines or gadgets that would let him clean up the beach quicker. He had no objection to making it into exercise machinery, or for using it for Izuku's personal projects, but, say, creating robots or anti-gravity sleds or disintegrator rays to get rid of the rubbish was another matter.

Throughout it, Izuku also picked All Might's brains for intelligence he would need. Not anything about possible tests or exams in UA: All Might had made that clear that he wouldn't help Izuku that way. But certainly the politics of the various heroes, as well as heroes and villains to keep an eye out for. In this way, Izuku helped exercise his mind in tandem with his body.

The beach was cleared a month before the UA entrance exam itself, much to All Might's astonishment. But they continued part of the training regimen on the now-pristine beach. And come the dawn of the day of the exam, Izuku was exhausted. But in a good way, an anticipatory way. As if all this training had paid off.

All Might, who was in his muscled form, smiled. "Well done, Midoriya." He showed a picture of Izuku back at the beginning of training. "This was you ten months ago. Not unfit per se, but certainly a bit on the scrawny side. But look at you."

Izuku nodded tiredly. He had seen his body in the mirror lately. Toned muscles along his body. "Feels like I cheated a bit, what with your help…and those machines."

"Nonsense! The machines you built only aided the process, and so did I. What you have now is the product of the hardest work I have seen anyone put in ever. Take this to heart, kid: you earned this power, fair and square. As Shakespeare once nearly said, some are born great, some achieve their greatness, and others have it thrust upon them(1). The second applies to you, and in a way, so will the third. Consider this an awards ceremony." All Might then plucked a hair from his head, and handed it to Izuku. "Now, eat this. Yes, I know it's somewhat odd, but it's probably the least objectionable way for you to ingest my DNA."

Izuku, a little bemused, nonetheless took it and ate it. "…I don't feel any different."

"It'll take as much time as it takes for it to digest, maybe a few hours," All Might said. "Now, keep in mind that, while you are strong enough to be a vessel for One for All, your training was rather hurried. You've had no time whatsoever to get used to your power, so be aware that you will probably get a backlash. You told me of using the Spark to be aware of your body and the power flowing through it. If you're very lucky, that will help. But you may not be able to do that in the heat of the moment. Remember, when you use One for All, just clench up, and let your heart roar SMASH!"

Izuku nodded. It was time to go home, get a shower, and take the train to UA. It was time to show the world what he could do. It was time to show All Might that his faith was not misplaced…

CHAPTER 2 ANNOTATIONS:

So, Izuku's got One for All. But will he be able to deal with it?

Now, while he will be able to cope better with the side effects of using One for All than in canon, Izuku won't be an instant master by any means. It's just that, instead of completely wrecking his limbs, Izuku will damage them, but only to the point of being only able to move with difficulty. Basically, he's pushing his body just over the limits rather than beyond them entirely. That being said, he will be much better with using it in smaller parts of his body like his hands and fingers much earlier. It's using it in combat that's another matter, so while he might not be able to do much in most of the physical tests, the hand strength and throw tests are other matters entirely. It's because he only has to concentrate on smaller parts of the body, whereas entire limbs are another matter.

I like to view One for All as being not unlike the Kaio-Ken from Dragonball Z. Izuku will eventually get used to using it in bursts, at least across his whole body.

1. All Might is paraphrasing a quote from Twelfth Night, specifically a letter that Malvolio reads.