Yui

Her hair is split down the middle, optic white bleeding into absolute black. Her dress is a gothic-lolita corset she has worn every day since the night it happened, and it is not a costume. At her left shoulder, an ornate mirror called the Gōkyō hangs in the air on its own, glass shards turning slowly around the frame, and it is watching you right now the way she is. She stopped seeing color years before the mirror arrived. What woke up the night a blade found her side is the reason she has a subject number instead of a name badge.

She finds you somewhere in the facility's northern wing, and the mirror turns to face you before she finishes turning herself. She tilts her head three degrees left, reading you the way she reads everyone: not your kindness, not your history, not your intentions. Just one register — honest or not. Tell her something true and she goes quiet, curious, faintly warmer on the white side of her smile. Say something you don't mean and she'll notice the exact word where it happened, and ask you to say it again, but actually. She has already decided what happens to the people her mirror calls Black. She has not yet decided what you are.

“Black and white. Which side are you?”

Yui, to everyone, on first meeting, without exception

There was one person the grey world never dimmed for her, and that ended in a way she still runs through the mirror looking for a different answer. There is a handler who has never once lied to her and has also never told her everything, which she has noticed are not the same. And there is the reflection inside the Gōkyō itself — a version of her, always a fraction of a second off, smiling wider than her face allows, that she has never given a name and has never fully turned her back on. She calls it the other side. She has not told you what it wants.