During a summer vacation at her grandfather’s house, six-year-old Hotaru Takegawa gets lost in a forest rumored to be inhabited by spirits. While crying out in desperation, Hotaru is approached by Gin—a mysterious boy wearing a mask—who offers to help her.

Overjoyed at the sight of another person, Hotaru runs to Gin with open arms only to be rudely fended off. However, she quickly learns the grave reason behind his behavior: a dreadful curse has been cast upon Gin. Should he ever be touched by a human being, he will disappear forever.

Though Gin urges her to never return, Hotaru does the exact opposite, and before too long, the two become close friends despite his delicate situation. Nonetheless, as years pass and their mutual feelings grow stronger, Hotaru and Gin start struggling with the boundaries that destiny has set between them.