I'm moving in with two of my friends in August with my cat Opal (F) who's around 4 years old. She's a Persian/munchkin mix and has absolutely no fighting bone in her body. I bring this up because one of my friends has a cat that's about 10 months old (M) and he's a tuxedo Manx cat named Fish.

For some context:  
Opal is such a friendly chill cat. She's very social, loves to meet new people and is pretty playful! She has no idea how to be mean, even when she's playing she doesn't use her claws and her bites feel like little pinches.  
Fish is a skittish cat, he gets really nervous when meeting new people and takes a bit to warm up to people. Because he's a kitten, he doesn't understand how to play with other people/cats so he does accidentally scratch.

So me and my friend have already introduced the two of them. Theres no crazy fights that's happening between the two of them but Fish won't stop chasing Opal around even when she hisses to tell him to stop. Keep in mind, I've never heard her hiss before and it's just a bit nerve wracking that the first time is with another cat. Opal also runs up and cuddles close to me every time Fish is chasing her and uses me as a barrier kinda between her and Fish.

I'm just a bit nervous that when we move in August, Opal isn't going to feel safe at home because Fish won't stop chasing her around and trying to hit her. She does seem slightly anxious every time they have a play date since she expects Fish to jump out of no where and start chasing her around again.

During their first visit Opal was very curious and exploring the place but once Fish batted her to play and jumped out to scare her, she started becoming less confident in exploring. It's just that we're unsure if we can comfortably leave them alone together when everyone is out of the place.

Has anyone had any experience with this? I've seen a lot of videos on introducing kittens to older cats in their homes but what's happening here is that my older cat is moving into a younger cat's home.

Please help if anyone has any advice. Me and my friend are just a bit stressed and don't know what to do.

Introducing two cats to each other