A young bioarchaeologist Yukisuke is attracted to a girl Koyomi, who runs a small stand of taiyaki pastry that he often buys. Koyomi is hospitalized, however, by a car accident on a rainy day after they go out together, and wakes up with short term memory loss, where she cannot remember anything beyond the present day. Yukisuke tries to live close to her as before but the lack of collective memory starts to stagger him.