
From what I understood yes those are just tattoo, but how I said in another comment I do believe that he is one of those "maggots" and he either didn't realize it or everyone except for the teacher knows. I do think it's more likely that he himself doesn't know it though and as someone else explained under my other comment it is a big possibility that we are right and Guwon ain't human cause there is a legend about Sisyphus who pissed off Zeus so much so that he decided to make everyone on earth unable to die (also creating zombies) and made him roll a rock (from what I remember from that explanation) up a hill for all eternity as punishment so there already are some similarities between the myth and this story
So About Guwon, is he something supernatural? Like a Frankenstein cus he got stitch marks around his neck, hands and feet, also Why's his arm all black? And he's eyes like a zombie? Are they all tattoos or I'm I just tweaking? Cus nobody's talking bout it lol