Raising Onee-san and the Cat

One day, on the way home from school. As the boy walks through the park as usual, there was

"Wanna sniff the kitty?"

A mysterious onee-san, and a cat being sniffed by the onee-san. Upon hearing her story, she apparently has no home and lives in the park... Feeling sorry for her, the boy picks up the onee-san and the cat and takes them home, to which his grandmother says one thing.

"You picked them up, didn't you? You take responsibility and look after them."