Keisuke's father has informed his mother, Keisuke, and Misaki that he has been diagnosed with cancer. Consequently, Keisuke announces his intention to inherit the family's liquor business and marry the daughter of his father's former colleague. However, Keisuke's sister, Misaki, does not give her blessing to the marriage. They are more than siblings. The two of them cross the threshold and make love all night, on the very day that Keisuke's fiancé's family comes to meet them. Misaki shows her desire for Keisuke, and they mutually surrender themselves to each other's flesh.