Smile's little sister.
Not much is known about her, but she's mostly depicted as a shy, quiet little girl by most of the fans.
Sister is a short little girl with long black hair and speculated to have red eyes. She has a dark gray tank top and brown shorts and pale skin. Some fans like to draw her with bandages on her ankles and having little three dots near her eyes for tattoos. She was also drawn by lol at one point with a kitchen knife.
- She will duck behind Smile when Sabitsuki brings out her iron pipe or fires her pistol. Possibly indicating that Sister is afraid of Sabitsuki and explains Smile's protectiveness of her.
- lol has a lot of drawings of her, or at least a girl who looks like her, in his pixiv gallery.
- In these drawings, she is often seen wielding a kitchen knife.
- One of said drawings was named also "Sister"
- There are theories going around that possibly indicate that Smile and Sister are related to Sabitsuki either by blood or just relation.