Sister - .flow

Sister

Characters » Sister

^Sister

Sister is a small black-haired girl found in a house in the Neighborhood.

She is seen holding onto Smile, and hides behind him if Sabitsuki brings out her Iron Pipe or fires a warning shot from the Handgun. She does not react to the Whistle, and cannot be killed as Smile takes the hit instead of her.

Trivia

Sister shares the same sprite sheet as Smile, and she is not named in the game files or code. However, the switch that controls her hiding behind Smile is named "Smile siblings behavior control" (smile兄妹動作制御), which indicates that she is Smile's sister.
lol has several drawings of a girl that looks like Sister in his pixiv gallery. One of said drawings is also named "sister". She is often seen wielding a kitchen knife.¹ This girl is actually the protagonist of a .flow prototype, and eventually she was replaced by Sabitsuki.² It is unknown if that character became "Sister" or if the "Sister" character is a reference to this girl.