The only pitiable part of his backstory is that he was unfortunate to be born in gangster family.
Contain spoilers for next chapter
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In the next chapter the flashback continues and he comments how he has never been treated like this before. So this was first time he was treated like that so not much on kids being mean to him. As we seen in this chapter, he didn't seam to care about his fathers petty affairs,out of jelosy and inferiority complex, with JS group but the resentment towards it came naturaly to him because of his fathers behaviour. So when that in the bathroom happened and he found out who Seungeon is he took in on his fathers footsteps.
Idk call me cold hearted but I am trying to pitty him but I can't. He seemd like a spoiled kid. It doesn't look like he was being mistreated by his father in any way. As I said the only pitibale ? part of his life is he couldn't choose not to be born in gangster family.
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Seeing people surprised this turned dark is so funny hahaha like bruh he pulled teeth of some guy with a pliers I am not surprised at all. I saw the forshedowing when he was talking about killing Seungeon and then hallucinate the menager is Seungeon and the way there was focus on the knife in chap 33 so maybe thats why I was not surprised at the turn of the events ahaha.