I don't think the "parents" we met were his real parents, at least not the dad.
His name used to be Do Hyun Su. Now it's Baek Hee Seong. There's a girl, one we can assume was killed, named DO HAE SU-the reporter has her necklace and reminisces on her. The name implies she is our ML's sister. My initial idea, especially since someone tried tying him to something and murdering HIM as well, is that they were going to make him the fall guy for the real Baek Hee Seong's crimes perhaps OR maybe the real Baek Hee Seong killed his sister and he snapped... I think perhaps the comment "we're all in the same boat" by t he "dad" at the birthday dinner was blackmail-instituted ie the dad and his real son, the Baek Hee Seong guy, might be the real killers and this psycho happens to have proof or at least acts like he does...
We know he had to run out of town, and we know he was almost killed. Maybe those "parents" of his tried killing him and he could testify on them at any point/has some sort of evidence against them; maybe he's realized he cannot win the fight and settled for monetary security of a sort; maybe they're all in it together in some twisted way.
I also got the weird idea that maybe Baek Hee Seong and Do Hyun Su were HALF brothers ie the same mom, different dad hence her feeling of possession over him.
I'm loving it already. Shows like this make me think "yes, tvN and OCN really ARE sister networks, aren't they?!" :)