ok so I'm well aware the bottom right corner is a whole mess of fuck so. to explain:

Natsuki invented Kimura as someone she could pretend to be to get a second freebie when she was young, and then carried on the lie as it became bigger. Between Natsuki and Kimura, she only has one krookodile and zebstrika total, they just have different names depending on which persona she is at the time. To facilitate the pretense of being two people, Natsuki caught a ditto and trained it to pretend to be her male persona, hence why it's also called Kimura. So the Kimura without the hat is actually a ditto pretending to be a human.

Nate knows exactly none of this, so to him, Kimura is just a friend of his daughter's.

the games and show give plenty of evidence that a pokemon, particularly a ditto, could perfectly imitate a human, including intelligence and thought processes, which is why the ditto is on here as its own separate person.