Kimitachi wa dou ikiru ka

After Mahito's mother is killed during the firebombings of Tokyo, he and his father move out of the city to live with his maternal aunt—who is already pregnant with his new half-sibling. Struggling to accept both his mother's death and new familial situation, Mahito is harassed by a talking blue heron who promises that, if they go to a nearby abandoned mansion, he can meet his mother once more. Source: ANN