Your right, Ryan is just trying to protect Lucaon. But I think he's just playing into intro's game.
Think about this: Lucian is a time bomb and barely holding onto his sanity. He's improving because of his love for Kyon, but heartbreak can turn him into a zero.
So, bad guys plan (can't remember his name) send Kyon, a wimpy guy who would never actually hurt anyone but would garner affection and love, to Lucaon. Who would grow to love him. Then 'activate' Kyon and expose him as a threat. Meaning Kyon never has to do any physical harm, emotional pain-like abandonment could be enough. lucaon just needs to feel betrayed and will become a zero. Easy peasy, with no strings leading to the bad guy as the cause of Lucaon's insanity.
Also, Lucaon's parents were liked by a large group of vampires and servants, but their work for a cure undermined the evil groups plans and made them a target. There was a flashback that described how everything went down, but everyone involved is dead now, with no way of the truth ever being exposed.
you have basically said what I'm thinking
Y'all realize Ryan isn't the bad guy right? I mean sure, he's being a massive d*ckhead right now but he's not wrong. We're only angry because the story is being told from Kyon's P.O.V. We've seen things that the other characters haven't, so we know we can trust Kyon, but they don't. Correct me if I'm wrong but, Lucaon is Ryan's only remaining living family member, yes? So it's no surprise that all his decisions are centered around Lucaon's well being.
I mean, when he saw how Lucaon was getting infatuated with Kyon, he found it amusing and even pushed for further development on his part, because it made him happy to finally see Lucaon opening up. But really, it's all the concern of family. Like, as much as I want Kyon to come out clean to Lucaon, what's the guarantee that it won't actually cause Lucaon to regress back to how he was before or even worse? What if he thinks Kyon was plotting this all from the start? What if he thinks he was betrayed again? Really, right now Kyon is like a landmine in the mansion, one wrong move and it might blow all the development between them apart, because as far as Lucaon and Ryan know, Lucaon's family died because a servant decided to betray their trust [and they have no reason to think otherwise, because i don't remember who it was that said so, but apparently Lucaon's parents weren't even that well-liked]
So, as much as I would like Ryan to fuck off and let them do their thing, I do understand where he's coming from ┑(￣Д ￣)┍