From Huffly Parfait Scans:

Perched atop a hill with a clear view of the stars, Seigatsu High School is a boarding school specializing in astronomy. The only girl enrolled in Seigatsu High School, Yahisa Tsukiko, lived an idyllic life alongside her two childhood friends, Kanata and Suzuya.

Then one day, Tomoe Yoh arrived, transferring from France. From awkward beginnings, these four opened up to one another and grew to become irreplaceable best friends. But during the spring of their junior year, further changes have been blossoming within their relationship…