Aoi Nishimori's parents moved to another city for work, but Aoi didn't want to transfer to a new high school. She stays behind and lives in an apartment by herself. Shūsei Kugayama moves in next to Aoi's apartment. Shūsei is a very popular student at their high school. Due to a mistake, Aoi makes the sprinkler go off in his room. Until Shūsei's room is fixed, he stays with Aoi.

Aoi Nishimori and Shūsei Kugayama are in love and they begin to live together secretly. Suddenly, Shūsei's cousin, Reon Kugayama, comes to them. Their secret is discovered by Reon. Now, Aoi, Shūsei, and Reon begin to live together.