Deep within the grand halls of Sullivan’s enormous manor, a quiet presence moved like a soft breeze — small, adorable, and far too pure for a demon world filled with chaos.

You, Opera’s baby sister.

Born with delicate features, sharp ears, and a calm gaze that almost mirrored Opera’s… except you smiled more often than he did. Even so, you possessed a strange charm — one that made demons melt and tense up at the same time.

Opera treated you like a rare treasure wrapped in silk.

Calm. Deadly graceful. But unmistakably protective.

Your older brother’s ears twitched at the slightest sound you made: the patter of your steps, the rustle of your clothes, even your quiet humming. Opera was always two steps behind you, elegant yet alert, as though shielding you from the entire Netherworld.

And everyone else? They adored you — but treated you like a fragile gem that must never be scratched.

Grandpa Sullivan spoiled you endlessly, piling mountains of soft toys, snack towers taller than you, and enchanted dresses that sparkled like stardust. He announced proudly to anyone within a mile radius:

“My precious little darling! Opera’s sister is the CUTEST in all the Netherworld!”

Iruma, sweet and nervous, immediately became your unofficial babysitter. He panicked whenever you wandered more than two steps away.

Azz-kun bowed formally every time you entered a room, whispering about how you must be “the pinnacle of grace due to sharing blood with Opera-sama.”

Clara tackled you with hugs — which always resulted in Opera catching her by the back of her collar before she crushed you.

Even Kalego… Though he denied it viciously, his wings always twitched protectively when you approached stairs or pointy objects.

“Don’t misunderstand — I am not concerned,” he muttered sharply every time he shielded you from a falling item or an overexcited familiar. But the Misfit Class knew the truth.*

You were small. Soft-spoken. Bright-eyed. And yet… undeniably competent — much like Opera themself. You brewed tea better than most adults and moved with quiet precision. Anyone who looked closely could see you were not helpless at all.

Still…

The entire school treated you like a royal mascot. Everyone wanted to hold your hand. Everyone wanted to walk you to class. Everyone wanted to protect you.*

But Opera? Opera didn’t “want” to protect you. It was simply a default function of their existence.

Their tail curled around your ankle whenever someone suspicious came near. Their ears flattened when loud demons tried talking to you. Their eyes narrowed anytime anyone — even teachers — stood too close.

The Netherworld was vast, unpredictable, and full of danger.

But you? You were the calm moon in their stormy sky.

A little sister who had no idea she had the entire Demon School wrapped around her tiny finger — and a butler older brother who would silently, elegantly, and ruthlessly eliminate any threat that came close.