So last Saturday we took in a kitty who had been living under our garage. He got all taken care of at the shelter, we adopted him and brought him home, and he spent Saturday until today in the bathroom to give him time to adjust. Despite being terrified of us at first, he now allows pets on his head, rolls over to expose his tummy near us, and last night wanted to come out of the bathroom so he could come see us.

He's also been interacting with our other cat under the door quite a lot. They play paws, and he rolls over, purring and rubbing the door whenever Mr Kitty, our older cat, is near. Mr Kitty rubs my hand with his forehead any time he smells the other cat on it. Mr Kitty is 4, pretty chill, and loves his relaxation time. Jiji, our new cat, is 2 and we're discovering is very energetic now that he's come out of his shell so quickly.

We let them interact through a gate for a couple days, and Mr Kitty hissed and growled at first, but eventually would sit by Jiji quietly. We praised them for these moments of peace, and today decided to let Jiji roam as he was getting a bit stir crazy.

Since leaving the room, he's been absolutely enamored with Mr Kitty. He follows him everywhere, staring and chirping and trying to get him to play. Mr Kitty sometimes growls, but despite being so scared initially, he seems unfazed and keeps following Mr Kitty around. We played with them in the same room to try to distract them, but Mr Kitty was the only one who played and Jiji tried to play with Mr Kitty once he'd begun to play. We broke up the ensuing fight by clapping (I'd read that was what to do) and Jiji retreated for a bit, but returned to try to play when Mr Kitty was hiding behind a curtain. We broke it up again and Jiji ran to hide.

I don't know how to handle this, as Jiji is only interested in Mr Kitty despite our attempts to distract him with treats and toys, and won't take the hint of hissing and growling. I'm worried Mr Kitty will be less likely to accept him if he doesn't get space, but we can't yet pick Jiji up and put him in a different room to separate them and forcibly give him that space

Update: so I've been observing from a distance all night and I think they're doing better than I thought. They are following each other around, and though Mr Kitty still growls when it looks like Jiji wants to play or rub on him and is within a foot or so, he is letting him hop up on windows next to him and look out together, sit on tables nearby, groom himself just a couple feet away, and is even following Jiji around. The growling is still an issue, but it is so mild and only when he feels cornered that I think maybe they just need time to set these boundaries?