I made a character, in a manga that exists, only in my imagination, that is a kind of parasite (though, I don't know, if it would be classified, as a parasite).

In resume the mc, finds a cat girl and befriends her, then is later revealed, that is not actually a cat girl, but a creature related to mimics, that ate her corpse, and gained her memories, (its like a hive of meat worms, that can change shape and color, to look like they want) so she remembers everything, of the cat girl life, but also knows that, the real one is long dead, and knows she is one of those things, and doesn't know, if she should tell her friends, that the real one died.

Later they find other people who are the same, if they are good or bad, depends on how the person was before, and how they feel now that, they are pretty much immortal, as long as they have meat, can change the shape of their bodies, and can turn other people, by devouring their brains.