Seeing different things on television became her only pastime, and she once wished of doing the things she watched if she ever managed to recover. Within the indefinite time she stayed in her room, she was usually seen watching television. Due to this, she was paralyzed from her neck down ever since and has been taken care of by her mother. In the living world, Yui was hit by a car when she was four years old. Her upbeat personality is most likely inspired by her past life in the living world where she was paralyzed since she was four years old from head to toe.

She is also a huge admirer of Hisako because of her 'murderous' guitar rift. She usually tells the other SSS members that they're 'morons', mostly because under the surface she is actually quite intelligent. She is often flirtatious with others, and takes advantage of every opportunity she can. Even within the members of the SSS, she comes off as very excited and loud. Yui is an extremely bright, cheerful, crazy and wild girl who is known to be hyperactive and talks extremely fast. She also has two pointy teeth like a cat. Another particular trait of her is her 'demon tail' which seems to twitch and move whenever she is excited, happy, or emotional in any way.

She wears wings that are hidden behind her hair.

On her wrists, she sports single handcuffs with few slabs remaining on each (possibly, both parts formed a common pair of handcuffs).

Though they don't seem to be in use, she also wears garters on each thigh with the addition of black choker around her neck. She wears crossed black ribbons up to her knees and black boots. She wears the same uniform as Yuri Nakamura and the other girls, although her shirt appears to be small enough to see her tummy. They are held together by small cross-shaped barrettes. Her hair is two bunches tied up with dark red laces and two twintails on the sides of her face. Yui has long, pink hair and hot magenta eyes.

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