A high school girl, Sei Saotome, unexpectedly is transferred to an elite high school in Nagano prefecture due to her parents' house-moving. One day, she meets Mizuki and Taiyo, and is invited to join astronomy club with them. The personalities of two boys are completely opposite from each other: Handsome young boy Mizuki is very calm and he loves watching stars, while Taiyo has a difficult nature but his grades are always on top of the school. In this astronomy club, Sei, Mizuki and Taiyo struggle with sorrowful and impatient love-triangle...