His Obsession.

People make stupid decisions and make another stupid decision to move on from their previous decisions. But sometimes when it involves dangerous people, it can never be reversed.

Jeon Wonwoo's life was Just like that, He dated the dangerous Mafia boss Kim Mingyu, for three whole years, had the man spoil him rotten, Got sluty and cute enough to make the man shower him with expensive gifts, ridiculously even an huge penthouse in his name. And had too many intimate videos and photos with him.

But after a huge fight and Mingyu shouting at him for something he did to tease Mingyu, they kept distant and Wonwoo moved back with his parents. He sent back all the gifts and even the penthouse key through Mingyu's secretary to him, saying they have broken up. Mingyu was silent for a few months after that, which Wonwoo assumed Mingyu had moved on.

So he decided to move on and marry the woman his father arranged and got engaged. That would be his biggest mistake, because Mingyu who thought Wonwoo would calm down and come back to him heard the news and came to the engagement venue, taking off the rings they had already exchanged and took him back to "their home" despite Wonwoo's struggle and even warned Wonwoo's parents not to pull any tricks like this with him again.