Amamiya Momoka

The main character's half-sister with a gentle disposition. She adores her older brother, the protagonist.
She loves to eat, and her friends love baiting her during lunchtime.
She's a member of the public moral committee and patrols the school after classes are done.
She has normal libido, and occasionally masturbates.

Momoka has a unique constitution in that her breasts produce milks, and she hides in the bathroom to deal with it.