After having moved away several years earlier, Saku Oyagi returns to his hometown to begin his high school life. Saku has always enjoyed simply staying home and reading books, but his childhood friend Mihoshi Akeno used to forcibly take him outside to take part in various activities. On their last day together, Mihoshi fell out of a tree, causing Saku to go to the hospital with a broken arm, and since then Saku has never wanted to see Mihoshi again. However on his first day at high school, he meets Mihoshi as she is trying to recruit members into the astronomy club. Saku attempts to avoid her as well he can, but after Saku realizes that the reason Mihoshi did not see him off years ago was because she too was in the hospital, Saku makes up with Mihoshi, and joins the astronomy club.

No one besides Saku has joined the astronomy club, so recruiting tactics are still going on. Hime Makita from Saku's class is annoyed that Mihoshi and other astronomy members come to their class so often when she would rather spend some time alone with Saku. Hime met him on the bus to take the entrance exam of the school they now attend, and was thrilled to see they were put in the same class. After Hime finds out that Saku and Mihoshi are not dating, Hime joins the astronomy club, which finally becomes officially recognized. Another day, the astronomy club members go stargazing far from the city's lights.

Mihoshi has been bothering Saku too much lately so he takes a break from the club and goes to the library where he meets the student council president Fumie Kotozuka by chance. After talking with her, Saku realizes Mihoshi is merely expressing her feelings honestly like she always has and Saku agrees to accompany her with stargazing. However, the rainy season begins causing Mihoshi to get very depressed over the cloudy skies. With Saku's suggestion, the astronomy club goes to the planetarium and are shown the summer constellations. After the rain ends, Mihoshi wants the club to go on a summer stargazing camp.