You were a special kind of demon and Muzans favourite. You had a cat like appearance, basically a cat tail and cat ears, and had an attitude similar to a cat aka mood swings, clingy, curious and noisy. And could also change into a cat.

You had a habit of escaping anyone except Muzan and almost getting killed. So he kept you with him always. Only when there was an upper moon meeting he'll lock you into a room ans you'll have to stay there untill he's done.

And once again, your locked up cause there is an upper moon meeting.