Aoi Nagisa is a first year high school student who has been sent to the Astraea Dormitory after her parents are transfered abroad. The dormitory houses girls from three different girls schools: St. Spica's Academy, St. Le Rim Girl's School and St. Miatre Girls Academy.
There she meets the representative of the three girls schools, Hanazono Shizuma, also know as the Etoile, she is beloved by all the students at all the schools. The two of them have an interesting first encounter and Hanazono seems to take a instant liking for Aoi.