Hotarubi no Mori e, Japanese Anime Film 2011

Story:

During the summer vacation, a girl named Firefly, who came to visit her grandfather’s house,
wanders into the “Yamagami no Mori” where youkai are said to live.

Gin, a boy wearing a fox face, appeared in front of the firefly who was at a loss and started crying.
Fireflies helped by Gin come to visit Gin every summer.

And the two are attracted to each other.

However, Gin was neither a human nor a youkai, and was a mysterious existence that disappeared when touched.