Tsuma, Shougakusei ni Naru.

The story follows Keisuke Niijima—who lost his beloved wife, Takae, ten years ago—and their daughter, Mai. They have been in a state of despair since Takae's death. One evening, an elementary school girl visits the Niijima family claiming to be the reincarnation of Takae. At first they don’t believe her but the girl continues to give them information that only the family knows. Keisuke and Mai soon recognize her as Takae and the three begin to act together as a "family.”

(Source: Crunchyroll News)