Kou returns to Japan after a few years overseas to attend school and reunite with his older sister Kaoruko and osananajimi Ena. They are overjoyed that he is back together with them. Little did he know that they are quite well-known at school: Kaoruko as the Jeanne d’Arc Scientist and Ena as the Emerald-Eyed Witch. There’s a huge commotion now with him around and the student council leader Sayaka declares that she will disband any club that doesn’t have anything to show by the end of the month. This puts Kaoruko’s science club and Ena’s astro-divination club in danger. Of course, they come and ask Kou to help them!