A high school senior. 17 years old. Female. She has an older sister named Mayu. At school, she has many friends and serves as the student council president. She is popular with everyone. She has known the protagonist since they were small. She is like a big sister to him. She treats the protagonist like a child and is a kind, caring older girl. She views him as a younger brother and thinks of him as a child no matter how much time passes. She feels a normal sense of modesty and shame around other peers her age. No matter what happens, she never breaks her 'protagonist is just a kid' mindset.

24 years old. Female. A beautiful woman who is very popular with men. Yuri's older sister. A freelancer who occasionally helps out at the bathhouse. She sometimes sits at the attendant's booth. She has known the protagonist since he was a child. She jokingly tells him that 'babies get in for free.' A compassionate, big-sister type with a kind heart. She often gives the protagonist toys to play with in the bath. She loves both Yuri and the protagonist.

42 years old. Female. The proprietress of the bathhouse. She looks as youthful as someone in her 20s. Mother to Mayu and Yuri. She wears her hair in a bun and is always dressed in a kimono. She is in charge of the booth and managing the hot springs. During work hours, she is always somewhere in the bathhouse. A refined, elegant lady. She observes the protagonist closely. She finds it strange that Mayu and Yuri treat him like such a small child. However, she is a soft-hearted person who spoils her children. She ends up spoiling the protagonist too. Her educational philosophy is to encourage growth through praise. She makes sure the protagonist pays the proper adult fee of 300 yen.