He probably just felt like there was nothing else in his life and you can see how he regrets it when his son finds out but by then to him its too late ig
I am with you, both characters and motivations were severely underdeveloped. all elements were there, but nothing was really done with them. so it felt like those pieces of personal history were just kinda there and did nothing. therefore, everything that happened was kinda disconnected from the original character motivation, personal history, and story drivers...and then 8 years later they were kinda living ok, despite all that trauma and the desire to die and disappear??? really???? math is not mathing... yet, it could have been better developed, we can all see it.
I liked the story but I think the whole revenge thing is too far fetched. I just thought it’s a bit much for yeonjin to do all this and then kill himself as a sort of fuck you to his father. It wasn’t his fault as a kid what happened and I think cha wookung’s words would apply to him in the sense of not be involved with adult affairs and just be a kid. He overwhelmed himself with getting his revenge that even if he didn’t kill himself he still lost 8 years of his life with munhyeok and it’s a sacrifice that seems unnecessary. He should’ve taken the route his wife did of leaving and living her life with her sons. Obsessing over revenge and payback is just the downfall of these two main characters. They wasted these 8 years of being together for the sake of one lousy character. It’s better to detach yourself than to drown and be swept along. That’s just my take on it personally.