I've been reading raws even though i don't understand one bit because its super slow and full of cliifhangers. For those who can understand Korean or read the raws, I can see that Lark is definitely not human. For what I see he has an ability similar to Karne and that is to control Fire? Am i mistaken or what? Also Setz doesn't have an ability and his father thinks he is not his son?
I can't read Korean, but I've seen the raws. I think the fire ability you're talking about might be the spells they're going to be learning? (Wonder how they will explain the fact that Lark can cast spells even though he is human...?)
About Setz, when his father told him he didn't have any powers, he asked "are you really my son?" (or something like that), but I took it as a rhetorical question (like "how could a loser like you be related to me?"), not that he seriously has any questions about Setz being his son. I don't think I saw anything in the raws that looked like there was doubt about Setz's parentage...?