Hagiura Yuuna

A teacher who has lost her virginity to the protagonist and was preyed on by him on several occasion, she successfully fought back and got him transferred out of her school.
Compared to her sister Aina, she is more outgoing and enthusiastic.
She is adored by her student due to her friendly nature.
When she was a student, she made it to the national swimming championship, and is now the adviser to the swimming team.

She is a cheerful woman who drags her sister along, but inside she is naive and timid, and more reliant on her sister when things get serious.
Yuuna tries to forget about the past when she was trained by the protagonist, and she keeps it all a secret from her sister.
Although she outwardly rejects the protagonist advances, deep down her desire for pleasure ended up creating the complex feelings of love-hate towards him.