Hotarubi no Mori e - The Novel

Hotarubi no Mori e tells the story of a six-year-old girl named Hotaru Takegawa, who gets lost in a forest inhabited by a mountain spirit (god) as well as Yokai. She is found by a mask-wearing human-like entity named Gin, who informs Hotaru that he will disappear forever if he is touched by a human. Gin then leads Hotaru out of the forest. She returns to visit him over the next few days and become friends, despite limitations on their interactions. Although at Summer's end, she must leave Gin to return to the cities and her studies, Hotaru promises to return to visit him every summer. As the years go by, Gin hardly ages while Hotaru grows closer to his age. They form a budding romance for each other and one night, Gin invites Hotaru to a festival, but that fated day is sure to come.

This novel is based directly off the movie, Hotarubi no Mori e.
---Watch it--- (can be found on YouTube, etc.)