KissXSis
The story begins with Keita Suminoe, a male third-year junior-high school student studying for his high school entrance exams. He is living in a home with his older twin stepsisters, Ako and Riko, who share no blood relation to him, and they help him prepare for his exams. Even though he initially dislikes himself for it, he begins to become attracted to his two step-sisters, and his two parents encourage him to eventually get married to one of them.
Episode Summary
While Keita studies at school, Ako and Riko reminisce on when they started going to junior high, the first time they were apart from Keita. When they watched Keita perform athletics, they fell in love with him. Meanwhile, their teacher, Yūzuki Kiryū, eavesdrops on their discussions and begins to worry about what is going on with them. After studying, Keita runs into Ako and Riko at the shrine, where they were praying for his success. He remembers when he was young and prayed to marry both Ako and Riko, only to be told by his father that polygamy is illegal. Keita makes his wish and the three return together.