On the final day of summer vacation, Kokona is ready to spend some long-awaited time with her mother, but these plans are unfortunately canceled due to work. Opting to go outside instead, she takes a stroll down a familiar path - one where fond memories appear at every corner. Later, in the middle of autumn, Aoi and Hinata are looking through a scrapbook of their childhood. Snooping around in Aoi's room, Hinata finds that she has kept a strange acorn as a keepsake, but doesn't remember the reason why. As its discovery dwells on her, a wave of old memories comes forth, causing her to reminisce about a forgotten event from her childhood.