Oblivion Island: Haruka and the Magic Mirror

Haruka is a single daughter who lost her mother at a young age because of terminal illness. She continued to live with her father after that but time and the fact that her father is always busy with his work has created an emotional distance between them. When her mother was still alive, she received a hand mirror from her as a present and she treasured it a lot. After her mother's death, she started to forget about the mirror until she eventually lost it. One day, she decides to go to a local shrine and pray for the return of her lost mirror. It is there that she accidentally encounters a small masked creature which she secretly follows to the land of forgotten items.

Synopsis from Anime News Network