Freshman Enomoto Chihiro, called Happy Fortune by his friend, just transferred to Rikkyouin High School (winning the admission lottery). Chihiro lost his parents in a traffic accident when he was 10, and has been living with his older klutzy sister Shinobu since that time. Good at cooking and cleaning, he does all the housekeeping chores.

On the first day at school: It is love on first sight for Chihiro meeting Akiyama Tokino — a mushroom nut — in the school library. And Ritsuko Kubel Kettenkrad — childhood friend and student council chairman — has always liked Chihiro.

Here, at Rikkyouin High School, all decisions are made by the lot (kujibiki), and even students are chosen by lots for the entrance exams. This is the story of a one-year competition among the candidate groups (four partners) for the position as the next school government leaders.