beta
This is me just guessing stuff from the top of my head
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Guwon might be some intelligent type zombie or a mutant since in the first chapter when the building fell down Guwon got buried in the rubble but he survived, also I think he had some sort of mafia or yakuza job based on his tattoos but who knows.
And when it comes to jinwoo, I think he used to be abused by his father (he might have killed him out anger or by accident) I guess that's why he is having trouble remembering his past or not wanting to remembering it.. and I think that's why his body subconsciously tried to defend itself from Guwon in his sleep or when Guwon tried to touch him... plus him saying he is not right in his head and stuff can indicate to a dark past.
But that's just me letting out stuff out of my dome and I could be 100 wrong.