During Doremi and her friends' summer vacation, they visit her grandparents in the fictional mountains of Fukuyama, where they hear of a mysterious legend of Mayuri and Zenjuro, two star-crossed lovers that died in the Edo period. During the next morning, when they investigate the forest, the girls get lost and face the Curse of the Full Moon, which makes them unable to use magic. Meanwhile, due to a traumatizing memory, Aiko develops a fear of Doremi's grandfather.