Muroto Kouta

Kouta is the protagonist. He is a virgin geek with some of the best grades in school, standing at the top of his class year after year.

One day he meets Shiina Chieri, a classmate of his, in front of a convenience store. After helping her with her studies, he is then offered sexual favors as a way to thank him for his tutoring, but only on the condition that they don't have penetrative sex. He is immediately captivated by Chii-chan's revealing clothes, voluptuous body, cute face and promiscuous behavior, all of which only make him want to lose his virginity with her even more.

Despite knowing that Chii-chan has a boyfriend, he still develops feelings for her beyond mere sexual attraction. This results in him developing deep jealousy of Chii-chan's boyfriend, as well as suffering in fear of his feelings never being reciprocated.