Nitroglycerin. A heavy, oily, explosive liquid, colorless in its pure state, but deadly unstable. To the rest of the world, it's a dangerous compound. To me, it's what comes out of my pores when it gets hot.
I was sitting in my backyard, legs crossed in a lotus position, staring intently at the palm of my right hand. It was a humid summer afternoon, perfect weather for my new physiology. I could feel the sweat glands in my palms working, secreting that sweet, lethal substance.
"Ignition, oxidation, expansion," I muttered to myself, ignoring the toy truck lying forgotten beside me.
In canon, Katsuki Bakugo used his explosions mainly as blunt force. Large areas of effect, lots of noise, lots of smoke. Basically, a hand cannon. But I knew physics. I knew an explosion is just gas expanding at supersonic speeds. If you don't direct that expansion, it scatters in all directions. It's wasted.
I looked at the rock I had placed on the garden wall. My target. I wanted to replicate the AP Shot (Armor Piercing Shot). In theory, if I formed a circle with my other hand and concentrated the explosion through that reduced orifice, the force wouldn't disperse. It would become a lance of compressed air and fire capable of piercing concrete.
I raised my left hand, forming a circle with my thumb and index finger over my right palm, which was already glistening with a sheen of sweat.
Concentrate it, I thought, frowning with a ridiculous intensity for a nearly five-year-old. Don't let it expand sideways. Push it forward.
I felt the heat build up. The characteristic itch on the skin.
"Die!" I whispered out of habit (old habits of the body, I guess).
I released the spark.
CRACK!
It wasn't the usual dull BOOM. It was a sharp snap, like a whip breaking the sound barrier, followed by a blinding white flash.
"AHH!" I screamed, falling backward onto the grass.
I clutched my right hand, hissing in pain. The air smelled of ozone and singed flesh. I looked at my hand. The palm was red, angry, and right in the center, where I had concentrated the blast, the skin had bubbled up into an ugly white blister. My fingers were trembling.
I looked at the rock. It was intact. Just a bit of soot on the surface.
"Dammit..." I groaned, eyes watering from the pain.
I had forgotten Newton's third law. And the fragility of infant epidermis. By concentrating the explosion, I had also concentrated the heat and recoil onto a tiny point of my own skin. My five-year-old body didn't have the calluses or thermal resistance to withstand a focused shot without support gear.
The sliding door slammed open.
"Katsuki!" Mitsuki's voice sounded alarmed.
She appeared in the yard, wiping her hands on an apron. Her red eyes scanned the scene: me on the ground clutching my hand, the smoke dissipating, and the smell of explosives.
In two strides she was by my side, kneeling in the grass. "Let me see," she ordered, her voice losing its shouting tone to become serious.
I held out my hand, wincing. She examined it with a critical eye, frowning. "Idiot," she muttered, but without venom. "You tried to make a big one without warming up, didn't you?"
"I tried... to compress it," I admitted, feeling stupid.
Mitsuki sighed and picked me up like a sack of potatoes. "You're just like your father when he gets excited about his chemicals, but with my temper. Bad combination."
She carried me to the kitchen and sat me on the counter next to the sink. She turned on the cold tap and put my hand under it. The relief was instant.
"Listen well, brat," she said, rummaging through a high cupboard. "Your Quirk is amazing, yeah. But your skin is still skin."
She pulled out a large, expensive-looking jar. It was a glycerin and aloe vera-based moisturizer. "I sweat weird stuff too," she said, showing me her hands. They were soft, flawless, despite her being in her thirties. "Glycerin keeps us young, but it also makes our skin more sensitive to friction and dry heat if we don't take care of it."
She turned off the tap and patted my hand dry with a clean towel. Then, she applied a generous amount of cream over the burn. It stung for a second, then felt cool.
"You have to moisturize," she lectured, massaging the cream in with a gentleness that contrasted with her usual personality. "If your skin dries out, it cracks. If it cracks and you explode something, you'll blow your hand off. Got it?"
I looked at my mother. In the anime, she and Bakugo were always screaming at each other. But here, watching her bandage my small hand with expert care, I remembered she was the one who understood my biology best.
"Yeah, old hag," I mumbled, looking away to hide my embarrassment.
She gave me a gentle knock on the head. "Show some respect. And next time you want to try something new, tell me. I don't want to explain to the hospital why my son blew off a finger."
I nodded, looking at my bandaged hand. The AP Shot would have to wait. First, I needed tougher skin. Science was power, yes. But biology was the limit.