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.

Despite initially going to refuse, Saku ends up agreeing to help the literature club. Mihoshi acts cheerful without him there, but is still troubled by his absence. Meanwhile, the astronomy club has their hands full with making the planetarium. Mihoshi suddenly hugs Saku one day after school and rumors spread after some athletic club members see them together with Soma. Fumie becomes concerned that Saku has been helping the literature club too much and that he may be concerned about the rumors regarding him, Mihoshi and Soma. Hime gives Saku a journal she compiled about the planetarium's construction. Saku feels re-energized about the astronomy club and goes back to help.

Saku's astronomy club participates in a winter stargazing camp with the girl from Takami Girl's School, who also participated in the Autumn Stargazing Conference. Saku, Edogawa and especially Hime do not dress warm enough, and while Saku and Edogawa brought more warmer clothes, Hime cannot dress in layers with the extra clothes she brought. After spending the first day freezing, Hime goes out at night to go to a local convenience store, but it is already closed by the time she gets there and a blizzard is blowing in. Hime tries to get back to the cabin, but quickly gets lost. The others notice she is gone, and also suspect Mihoshi went out to search for her. With Hime close to freezing to death, Mihoshi finds her and the two wait out the blizzard in a small snow cave. They find they were not far from the cabin and while they are scolded for what they did, everyone is relieved to have them back safely.