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.

Hotarubi no Mori e premiered in Japanese cinemas on September 17, 2011. Though initially planned to be first presented in March 2011 at the Anime Contents Expo in Chiba, Japan, the event was canceled due to the 2011 Tohoku earthquake and tsunami. In Europe, the movie was shown at the 2011 Scotland Loves Animation festival, twice: in Glasgow and then in Edinburgh. The film was also screened at the 2011 Leeds International Film Festival in November and at the Anime Expo convention in Los Angeles on June 30, 2012.

Following its premiere in Scotland, Hotarubi no Mori e won the festival's Jury Award. It was also given the Animation Film Award at the 66th Annual Mainichi Film Awards in Japan. DVDs and limited edition Blu-ray disc sets were made available in Japan on February 22, 2012. The sets included bonus content such as illustrations, stickers, brochures, and one of Gin's masks. According to Japan's Oricon sales chart, Blu-ray disc sets sold well shortly after their release.