You were there, a focused look on your face as you practiced evasion maneuvers with Shoto Todoroki. A small, icy wall would spring up, and you’d dodge around it, Todoroki offering a quiet word of advice. It was the logical pairing, given his control over the terrain, but it made something hot and irritable coil in Katsuki’s gut. It was annoying. You were annoying. The way your focus never broke, the way you didn't even glance his way… it was all just… annoying.

He was so busy festering in his own irritation that he almost missed it. A sound like a vacuum seal popping, and a shimmer of distorted light in the center of the field. The classes’ exercises ground to a halt as a small figure materialized within the glow. A kid. No older than five. Spiky, ash-blond hair and a scowl that was eerily, devastatingly familiar. He wore tiny black cargo pants and a bright orange t-shirt with a cartoon explosion on it.

The kid blinked, his red eyes taking in the circle of stunned teenagers. His little fists clenched. “What the hell?” he yelled, his voice high but fierce. “Where the fuck am I?!”

A collective gasp went through the class. Izuku’s jaw was on the floor. Kirishima made a sound that was half-choke, half-laugh. Katsuki, his boredom instantly vaporized, scoffed. “The hell is this? Some kinda shitty prank?”

The kid’s head snapped toward the sound of his voice. Those crimson eyes widened in recognition and pure, unadulterated relief. “Daddy!”

Katsuki’s brain short-circuited. “HAH?!”

Like a rocket, the kid shot across the field and latched onto Katsuki’s leg, small arms wrapping tightly around his calf. He buried his face in the fabric of Katsuki’s pants. “You look… smaller,” the kid mumbled, confused but unwavering in his certainty. “But you’re still you!”

Katsuki stared down, rigid with shock. He looked like a man who had just been told gravity was optional. “The hell… I’m not your… what the actual fuck?!”

Aizawa’s voice cut through the murmuring, tired but firm. “Bakugou. Language. There is a child present.”

“Looks like he already knows all the good words!” Kaminari whispered, earning a sharp elbow from Jiro.

Katsuki ignored them, his mind reeling. He awkwardly patted the kid’s head as if trying to disarm a bomb. The kid just beamed up at him.

It took a few minutes and a quick call to the principal to theorize what had happened: a villain’s time-displacement Quirk, temporary but stuck on a cooldown. They were stuck with him.

The initial shock wearing off, the kid looked around, his brow furrowed in a perfect mimicry of Katsuki’s own thinking face. “Daddy?” he asked, his voice smaller now. “Where’s Mommy?”

Katsuki stiffened again. Right. A kid implied a… mommy. The concept was so abstract and terrifying he felt his palms sweat. “Who… who’s ‘Mommy’?” he managed to grit out.

The kid looked at him like he was an idiot. “...Mommy.”

Katsuki’s eye twitched. He could feel the heat of twenty pairs of eyes on him. “Her name, you little gremlin! What’s her actual name?”

The kid pondered this for a second, his nose scrunching up. “You call her ‘Sweetheart’. Or ‘Woman’ when you’re being grumpy.”

Katsuki’s entire face flushed a spectacular shade of crimson. “I DO NOT!”

“YOU DO!” the kid yelled back, fearless.

Just then, you finally broke away from Todoroki and wandered closer to the commotion, wiping a bit of sweat from your brow. You’d been on the far side of the field and had missed the initial spectacle. The kid’s head whipped around. His eyes landed on you. His entire face lit up, the scowl vanishing, replaced by a joy so bright it was almost blinding.

“MOMMY!”

Before you could take another breath, the small blond tornado detached himself from Katsuki’s leg and launched himself at you, slamming into your legs and wrapping his arms around you in a death grip. “Mommy! I found you!”

A beat of silence. Then, a snort. It came from Mina. Then a choked giggle from Kaminari. Soon, the entire class was struggling to hold back their laughter, the dam of tension breaking all at once.