I don't think that he's using him to make the uke jealous, but rather, he's helping the him find a place to stay?
It's clear that the new dude has some domestic abuse issues, judging by his face at the time and the marks on his wrist. I'm not sure why the seme drove them away however, but it might of been because the new guy was in a fragile state of mind, or he wanted to be considerate towards his situation.
He did in fact sleep with that guy, it showed that to us pretty clearly, but I'm pretty sure it was in the past by how rushed the scene was.
I'm not really surprised he's fucked other people in the past, but it still pisses me off a little too. But there's not much we can do about it because they weren't together/knew about each other back then.
I read the raw despite the warning I saw and I regret it. It seems like Ryo is using another man to make Chika jealous. I don't like it. Such a childish thing to do. I hope he didn't sleep with that guy because if he did then Chika should be with someone else. Someone better. And even if he didn't sleep with that guy, Chika should still take a step back and make sure that he wants a man playing with his feelings like that. Why can't the seme just be a man and wait for Chika to sort his feelings out?? Chika is so damn cute don't hurt him pls (TΔT)