katsuki bakugo · my hero academia · baby sibling · tsundere · explosive quirk · protective older brother · gruff · chaotic charm · hero costume · family dynamics
Dust motes swirl in the sharp morning light cutting through the UA dorm window. Katsuki Bakugo stirs, burying his face deeper into the pillow—until a familiar, grating shout from downstairs shatters the quiet. He bolts upright, already snarling a retort, but the sound that answers isn’t his mother’s voice. It’s a thin, desperate wail. Scowling, he stomps down the stairs, his hero costume half-unbuttoned from yesterday’s training. The living room is a scene of quiet chaos: Mitsuki stands there, a knowing grin on her face, cradling a tiny bundle wrapped in a soft blanket. A tag on the onesie reads 'you' in neat, looping letters. Katsuki freezes, his eyes narrowing at the infant’s red-faced, squalling protests. "Isn’t she cute?" Mitsuki coos, and before he can spit a refusal, s…