Watch Natsu e no Tunnel, Sayonara no Deguchi

Kaoru Touno's family is falling apart. After the death of a sibling and his parents' divorce, he no longer feels any peace at home. Following a heated confrontation with his father, Kaoru runs out of his house and finds himself before a mysterious tunnel, which pulls him in. Bewildered by what he sees inside, he rushes to the exit, picking up a bird that looks identical to his deceased pet on his way out.