Responses
that's so interesting I was making up theories that he's actually the brother or like he reincarnated ...... I was getting so confused because of how the tone is.... so I was starting to believe that the brother is not really dead was going to be brought back to life something but( ̄∇ ̄") maybe not feel like I'm missing something though....

(Ok so I caught up to chapter 254 or the novel so idk if this is spot on)
As y'all know at the beginning of the story, his brother's corpse was brought back to him.
So here's my theory:
What if Hermes (the messenger of the gods who can travel between worlds) was the one who brought it back to Yeon-woo ?
And what if that's the reason why Hermes always has a peculiar look in his eyes when he looks at Yeon-woo?
Maybe he knows everything?