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)This is a very taboo story about incest and love between twins. Yori's attitude has changed. He and his twin sister, Iku, used to be inseparable as children, but lately Yori has been different — eager to be way from Iku. Iku worries that he hates her, but the truth is far more scandalous. Now, Yori would risk losing everything to have his little sister. Iku loves her big brother enough that she would never risk losing him, and so she will do what it takes to keep them together... but Yori does not want to have her that way — as a sister dedicated to her twin. Can Iku ever love Yori not as a brother but as a man?