I'm so glad you're enjoying the game :)
In the current public release, the only hookup option is Leo. The next release will be the frat party, which will add two more hookup options. The release after that will be the club, which will add three more.
I'm just about done with the frat party update, so it'll go into early access pretty soon. I'm creating the hookup CGs right now, and there are a lot to make 🙂 I put a preview of one of the CGs on Twitter—you can probably guess who one of the hookups is even with it being cropped & censored...