During her last summer vacation of high school, Ayano had traveled alone from Tokyo to Kyoto to search for her best friend, Mirai, who had disappeared. Before summer vacation, the shy Mirai had been confessed to by Katsuragawa, a classmate and the most popular boy in school. Although they started dating, Mirai consulted Ayano about everything related to their relationship. Ayano, not wanting Mirai to get ahead of her, had given her virginity to an older university student, Shun, but ended up getting pregnant, which caused her to treat Mirai coldly. Ayano suspected that she might be the reason Mirai had run away from home.