Kitty to Mimmy no Atarashii Kasa is an anime film that premiered in winter 1981.

About the production: the story comes from an original script, the film runs about 24 minutes and its current status is "finished".

Hello Kitty franchise's first puppet animation work. Kitty and Mimmy are twin kittens. Two of them have been staying inside on a rainy day get a souvenir from mother who came home; an umbrella with different colors and boots. The two are delighted, but rain has stopped. Kitty and Mimmy wish for rain again to go out with an umbrella, despite the good weather the next day. The long-awaited rain will soon come. Note: The stop-motion short theatrically released alongside Unico, as well as bundled with the movie for a DVD release.

Official synopsis from AniList.