Akira's father, an archaeologist, has remarried, giving him a new stepmother and three stepsisters, Yuki, Nana and Miu. While on his honeymoon, Akira's father makes an archaeological find and decides to stay on site in order to supervise and leaving Akira at home alone with his new family members. After being discovered in bed with Yukie, his stepmother, Akira finds a box containing a scroll and three bottles. Using the knowledge his father taught to him, he reads the Sumarian language on the scroll and finds himself in a contract with the goddess Inana, who tells him to collect the love juices of his sisters in the bottles before the next full moon or else a terrible horror will befall him. (Source: ANN)

Shinya's school days are boring until Akane, a woman that his brother was to marry due to a family arrangement, started attending the same school that he was attending. Shinya remembers meeting Akane when they were younger and that they made a promise to be together when they were older. In order to make Akane, his and his alone, he gets his sister-in-law to teach him everyway possible to please a woman. After he approaches Akane, and they begin to make love, the gradual distance between the two begins to close and affects everyone around them...