Responses

No, I don't think there's anything wrong with him- per se. I think he uses the sunglasses as a fake persona to troll everyone. Because during the manga, he acts super childish and babbles a lot. But at times, he gets serious and talks normally. But then hides behind the babbling persona again.
As XxRedIrisxX said, Yuri is smart and at the top of his class.
does yuri have a mental disorder? like autism or something? i mean the way he talks and acts makes me wonder.. or is he just like an airhead?