1.

Chakra, he learns early on, is just a broken ass Quirk. Theoretically, it can do just about anything, imitate any power he can think of, and it's only generally limited by imagination and how much work one is willing to put into wielding it.

He knows what hard limits it's supposed to have. For example, shinobi are supposedly more naturally inclined to certain elements, meaning that other elements are much harder to master. Thus, a lot of shinobi can only use one or two elements, and those who can use more than that - or all of them - are few and far between.

All Katsuki hears is that, as usual, most people settle for whatever's easiest, giving up at the first roadblock on their path, listening to other people when they say no, you can't.

In contrast, Katsuki's response is always, without fail, fucking watch me.

2.

"I didn't do anything wrong," he says, stubbornly, glaring at nothing in particular but imagining it's his parents' disapproving faces.

Shisui snorts, incredulous. "You set yourself on fire."

Katsuki rolls his eyes. "I had it under control."

"On! Fire!"

"It's not something to freak out over," he insists, because it isn't. Katsuki has always had complete and total control over his body and his Quirk. He spent an entire childhood fine tuning that control until he could change every aspect of his explosions - heat, strength, light, the density and quantity of smoke - and move and contort his body into just about every position. He stretched and worked out and trained until his body could withstand being thrown around by explosions, until he could launch himself into the air and maneuver just as smoothly as on land, until he could jump and twist and fling himself and fight on instinct alone.

Up until he got into Yuuei, he had to figure out his Quirk on his own. Most of the hero kids were in the same boat. Quirks were an intrinsic part of society, but studies into them were still ongoing, inconclusive. A lot of their hero courses were figuring out the mechanics of their Quirks and how to use them in new and efficient ways, taught by other heroes who had gone through the same thing.

He's used to not having precisely defined limits and having to define and redefine them for himself, every time he discovers a new facet to his powers, a new perspective on things. He won't know what he's capable of - or just as important, what he used to be capable of but is no longer - until he tests it out in a controlled setting, over and over until he's got enough results to form a conclusion. He won't be satisfied until he has the same total control over this body and power as he did before, until he's back up to the same level of skill and precision, until he's the strongest and stronger still.

Which is all to say that Katsuki knows what the hell he's doing, and he doesn't appreciate all the flack he's getting just because this one time he miscalculated and set himself on fire. It wasn't even a large fire, and he put it out immediately, not at all helped by Shisui freaking out and flailing uselessly over him.

Why they keep promoting him, Katsuki will never know.

"Your brother is going to stab me in the kidneys and smile politely as he watches me bleed out in front of him, do you understand? He will cut out my heart and feed it to me! There's no way I'm letting him know his precious baby brother was put in harm's way on my watch," Shisui tells him, looking a little wild-eyed.

Katsuki shrugs. "I won't tell him if you don't." Worse than the cold-blooded murder Shisui is dreading is the mental image of his brother finding out about this and giving Katsuki his I'm-not-mad-just-disappointed face. As Bakugou, it was never his mom's shrieking that got through to him, but his dad's pointed silence, and that hasn't changed in this new life. He can ignore Fugaku's exaggerated disapproval, but one glimpse of Mikoto's cutting civility or Itachi's quiet disappointment, and Katsuki just, fucking crumbles. He can't handle it. Refuses to, actually, which is why he's not above blackmailing Shisui into keeping this a secret.

"Ugh, fine. But if you rat me out, don't think I won't take you down with me!"