Hana is a high school student who has come to Tokyo to take an entrance exam. During her stay, she is taken in by the Nakano family, who are relatives of Hana. The Nakano family has a son named Tadashi who is a dull student who is retaking entrance exams, but instead of studying, he spends his days masturbating in front of his computer. One day, Hana and Tadashi meet again for the first time in several years, but... while they hadn't seen each other for a while, his cousin has evolved into an unbelievable bust! Taking advantage of the fact that they used to often take baths and sleep together, Tadashi makes a move on Hana's breasts.