Actually, Niel did say that he was interested/ in love with someone and didn't want to get into the same misunderstanding due to not communicating as he did with Eugene in the past. That was when he met Eugene in Eugene's Uncle's bar. So Eugene does know that he already likes someone else.
Was about to say
You can't really compare rissa with Eugene. Rissa was really annoying before. I get it that she didn't have any idea about Niels sexual orientation but she continuously talked about things which clearly reflects her heteronormative mindset. You can't expect from readers to accept this kind of behaviour while reading a bl manhwa. And about Eugene, Niel clearly said he does have someone in his life. If he is only trying to get his old friend back, it's not a big deal. We still don't know his motives yet. And I really didn't find any comments where someone is willing to kill Eugene
Ah, I missed that line on my re-read. But still, Niel says they're having issues and Eugene says go fix it and be happy. Jensen might jump to some conclusions, Eugene might make amove - we'll see. But that doesn't make Eugene a horrible stalker that needs to go die already.
So far, all Eugene did was find his social media and you guys are ready to kill him. Kind of like you were with Rissa. Niel didn't tell him he was interested in anyone, so as far as Eugene knows he has a chance to fix the huge mistake he made when they were both idiot teenagers.
Niel got his closure, admitted he loves Jensen - they're pretty solid at this point and the author doesn't seem like the type to drag drama out too long. Eugene might cause a little turmoil, but it's gonna work out - hopefully with a fresh relationship for both Rissa and Eugene so everyone's happy.