With Slime

After a time-space collapse, Earth has merged with another world, and under its influence, humans have evolved magical powers.

So it's not at all unusual for Honda, a perfectly ordinary human, to have a friend who's a monster hunter. What is unusual, though, is for said friend to come back from a dungeon crawl with a pet slime for Honda.

The slime is a wonderful pet which looks cute, can clean the house, can even heal... and which happens to feed on something extremely specific.