Toume Yuu

The main character's first love in middle school. She is married.

Ever since she was cheated on by her boyfriend, she has been sleeping around with an unspecified amount of partners, switching from one to another.

She is easy-going and does not take things too seriously. She used to have sex with her partners such as Matoba in a way that she took the initiative, but through her activities with the main character in the circle, she comes to realize that she is a true masochist.

She enjoys swapping with the protagonist more than others because sex with someone she knew in junior high school, increases her masochistic embarrassment.