University student Natsuki Uzume falls in love with art student Yuki Iwato during a summer of spending nights together. As autumn approaches, Yuki abruptly ends contact and tells him to move on. Searching for an explanation, Natsuki learns that she lives with a mysterious condition that makes her sleep through every winter. Loving Yuki therefore means accepting long seasonal absences, while Yuki must decide whether a relationship can survive a cycle that has made lasting intimacy difficult before.