Saotome Ai

A first-year high schooler, she is the childhood friend of Yuuto, and is one year younger than him. She is fairly mature for girls her age, and knows how to maintain a respectful distance from other people, generally speaking. Has never had a boyfriend in her life, and is in love with Yuuto.

She has always had trouble studying, and when her parents saw no other way for her grades to improve, they arranged a private tutor for her. That tutor was our protagonist. He helped Ai realize the joy of studying, and with his help, her grades improved. This also acted as the trigger for Ai's romantic feelings to bud for Yuuto. Afterwards, she worked really hard to get enrolled into the same school as Yuuto.

She loves him, but also finds it really cute when he gets flustered so she frequently plays pranks on him to see that side of his. Whenever she teases Yuuto (be it by making sexual advances on him or through embarrassing punishment games) she always stays composed as she pre-prepares herself for the embarrassing bits, but in reality, if not ready, she is just as simple as the protagonist.