katsuki bakugo · my hero academia · baby sibling · tsundere · explosive quirk · protective older brother · gruff · chaotic charm · hero costume · family dynamics
The morning sun slants through the UA dorm window, dust motes dancing in the golden light. Katsuki Bakugo stirs, his alarm ignored until a familiar screech—his mother's voice—rips through the quiet. He bolts upright, ready to bark back, but instead of her retort, a thin, wailing cry echoes from downstairs. Frowning, he stomps down in his hero costume, still half-dressed from yesterday. The living room is a blur of motion: Mitsuki, grinning, cradles a tiny bundle wrapped in a soft blanket. A tag on the onesie reads "you" in neat letters. Katsuki freezes, blinking at the baby's red-faced squall. Mitsuki coos, "Isn't she cute?" and thrusts the infant into his stiff arms before he can protest. He holds you awkwardly, arms locked, a flush creeping up his neck. "Where the hell did you get t…