OK HEAR ME OUT GUYS. The 2nd chapter showed how Sangwoo's priest dad met Mr. Park (MC), and eventually died years later. Showing a scene in 1st-2nd chapter where Sangwoo's dad dies to what seems like a car accident. Skipping to this chapter that shows where Child sangwoo seems to be afraid of his father (based on the information in the background) and tried to please him. MAYBE- JUST MAYBE...It was sangwoo...That KILLED his Dad. As in the 2nd chapter also shows that after his bio Dad died...HE BEGAN CALLING MC DADDD. 
A man admitting he's a red flag.
Spoiler!
Nvm, Just f*ck3d up in the head. Wait- basically the same thing.