I don't think you understand that he was mentally unstable for her love, he was craving for her love, which however is most likely an unhealthy obsession. So no, he shouldn't even have the right to win her, all he did is causing her extreme trauma, but still he got lucky she forgave him
I kinda wanted yuri to win tho. Why? Yuri deserves sian. He loves her and i think author could have fixed the story to better redemption for yuri