Hotarubi no Mori e

Also known as:  Into the Forest of Fireflies' Light, The Light of a Firefly Forest

The anime film Hotarubi no Mori e is created by studio Brains Base, based on a supernatural romance manga by Yuki Midorikawa (Natsume Yuujinchou). The story centers around Hotaru, a little girl who gets lost in an enchanted forest where apparitions reside. A young boy, Gin, appears before Hotaru, but she cannot touch him for fear of making him disappear. (based on ANN synopsis)

Permalink: anime-1257

Producers, official website and other details: AniDB, ANN, Wiki