Anon comes across a deformed Marisa that was cast out of its clan, and takes it in along with another Marisa that was nearby. The deformed one can't talk well, but it's well behaved, doing its business cleanly and imitating his eating manners. On the other hand, the normal Marisa is messy, and gradually starts acting like scum, making demands of Anon for a yukkuri to refresh with.
One day, just as Anon is planning to throw out the normal Marisa, his friend comes by, and takes an interest in the deformed but intelligent Marisa. His friend offers to do an operation that switches their paste cores, and Anon accepts.
The bad Marisa wakes up first, already thinking of Anon as scum, and makes unintelligible noises, though it doesn't realize it. Anon abandons it outside, telling it to find its own yukkuri to refresh with, but showing her new look before he leaves.
The good Marisa is happy that she can move better and speak well enough for Anon to understand, and thanks him. She eventually gets a silver badge, and the story ends with her welcoming Anon's friend to his home.
Illustration: post #21524