Just wanted to put some insight down for Yuri. Before diving in I'd like to say yes he is an asshole right now - it's sorta, hard for me to read. and no, his past is not a pass for him to be able to do this shit. But I hope this may give some insight as to why he is this way.
I can't exactly speak for his circumstances, but from my experience, emotional abuse from my family has kinda broken the concept of love and family. Blood relationships mean next to nothing to me. I honestly can't say whether what Yuri has is truely romantic love or not; it could be jealousy/fear/anger of his most important person being taken away. But if there was someone - anyone, during my childhood who was just as genuinely kind as Yuri's sister was, I think I may have latched on to them just as he has. when the people around you treat you like absolute shit I wouldn't find it strange that Yuri became so attached her. Yuri was not brought up normally, he is a victim of family abuse - he needs therapy and time to heal. So expecting him to suddenly do a 180 overnight and suddenly change as a person is unfortunately unrealistic.
I think I had more to say but its late and I can't remember or think very coherently so ill stop here lol
Lmao I can't take this seriously