The Record of a Tenement Gentleman [1947]
In post-war Japan, a man brings a lost boy to his tenement. No one wants
to take the child for even one night; finally, a sour widow, Tané,
does. The next day, complaining, she takes the boy to his neighborhood
and finds his father has gone to Tokyo; it seems the boy has been
abandoned. Tané wants to leave him there, but he follows her home. The
next morning he disappears fearing a scolding after wetting the bed.
Tané realizes she likes having him there, searches for him, and keeps
him when he's found that night. Within days, she considers him her son.
in IMDB