Machida Hina (Aya Ueto), who is studying at the private Hyuga Girls' Senior High School, met a girl of the same grade, Akako, in the health room. That night, they went to the downtown area to have fun. After separating from Akako, Hina went to the video game store alone and met a man, Koga Ikumi (Naoto Fujiki). Hina was attracted to him and followed him to the restaurant for dinner. She claimed to be a 20-year-old beautician and later went to his house together. Then Hina wanted to go back, and Ikumi hoped that she would stay. That night, the two slept in the same bed, but did not have sex. The next day, a new math teacher came to the class. Hina was surprised to find that the teacher was the man from last night, but he did not recognize Hina. Because of his handsome appearance, Ikumi was very popular in school and was invited to serve as a consultant for the swimming club. That night, the teachers took him to a dinner party in the downtown area. But Ikumi was not interested in all this, he had his own secrets. At the same time, Hina finally guessed Ikumi's email address, and she sent him a message for help...