Natsuki is not like other girls. She has a magic wand and a transformation mirror. She could be a witch or an alien from another planet. Together with his cousin Yuu, Natsuki spends the summer in the wild mountains of Nagano, dreaming of other worlds. When a terrible series of events threatens to separate two children forever, they make a promise: to survive no matter what.

Natsuki has now grown up. She leads a quiet life with her husband and tries to survive by pretending to be normal. But the demands of Natsuki's family grow, her friends wonder why she is still not pregnant, and dark shadows of her past haunt her. Fleeing from the suburbs to the mountains of his childhood, Natsuki prepares to reunite with Yuu. Does he remember their promise? And will it help to save it?