As far as I can tell - but I can't read Korean sadly - it's not gotten explained until the most recent chapter (106).
Probably Spoilers!!!!
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Satan came to visit him "inside his mind", stopping the smaller demons for a while to talk to the real Sid. He made his promise to give Sid a good position by his side if Sid betrayed Cain, but whatever Satan had actually planned for Cain, as far as I got it, Sid did not play along.
To me it still seems like there is plenty going on which the author is not explaining and it still seems to me like Sid's "real plan" is not yet disclosed. There are hints that he is afraid for Cain and wants to save him??? But that's only part of him? Hard to explain ^^
Seems like it's gonna go pretty decent (kinda-) guess I'll wait for Sid's redemption arc or a possible self-sacrifice, explaining yourself to one of the other MC's somewhat death
I just speedread this and I get the Sid hate, he's an ass, yes. Dunno why, I can't bring myself to hate him, but if he does die I wish he has a quick painless death.
Does it ever get explained why Sid had the multiple guests in his body or how he ended up meeting Satan or nah?
I think I wanna read this on an official website after this 'cause seeing Sid just exist hurts my heart even when my favorite character is Rice Cake