We never really find out for sure. It's all up to interpretation. He basically wants to hurt her so bad he'll leave a scar in her heart and will always be a part of her. Personally, i think it's incestuous. Either way, he's a freak lol.
yeah to add on to the previous reply I personally think that he is obsessed with seeing her cry again like in the past. when she started saying "don't go" to dion I think he thought she was gonna cry so he stayed. but perhaps there is a chance he loves her incestuously lol
i read somewhere that it was because he was so used to being emotionless that when he saw roxanna cry over her brother's death, it was the first time he witness someone crying over someone else so now hes obsessed with her bc shes the only one who has shown him an example of 'human' emotion
Rest in peace hyungdo's asshole 2021