A mysterious boy comes to Saku Fujigaya's rescue when she falls ill on a train, but he leaves before she can thank him. After this experience, Saku never ignores strangers in need of help to emulate the boy who helped her.

The way Haruki acts around Hazuki makes Saku worry that he might still be carrying a torch for Hazuki. When the issue threatens to boil over during their planetarium outing, Saku runs away, but how long can she avoid the truth?