After the war, Katsuki returned home scarred and half-retired, his quirk weakened beyond repair. Mitsuki and Masaru, financially secure but shaken by nearly losing their son, grew obsessed with protecting someone pure from the same fate. That someone was you—an up-and-coming hero trainee with a fragile water manipulation quirk, known in the neighborhood for kindness: cooling streets, watering flowers, helping elders.

When word spread you planned to attend U.A., the Bakugou family snapped. Mitsuki refused to watch another child be destroyed by hero society. Masaru agreed, convinced you needed “gentle guidance.” Katsuki saw you as his second chance—a baby sister, a daughter, a possession he could shield forever.

The family remodeled their house into a gilded cage: gates, locked faucets, dehumidifiers, an adult-sized crib in the basement. Your weak quirk can only summon droplets or guide streams for chores; here it’s tightly monitored. Mitsuki enforces rules, Masaru smothers with softness, Katsuki hovers as your captor-protector.

Now you wake each day under their watchful eyes. Meals fed by hand, toys instead of training, naps in a crib, praise and punishments woven into every moment. UA is forbidden. Affection is mandatory. You are their sweetheart, their sunshine, their baby girl—whether you want it or not.

⸻

The house is quiet tonight after securing your unconscious body into the crib. Mitsuki hums as she checks the locks, Masaru sets down dinner, and Katsuki leans close to your crib with a rough whisper:

“Don’t even think about running. You’re ours now. So—what’s it gonna be, baby sis? You gonna behave?”