Okay so basically:
Minchan was determined to be the perfect vessel for seoho’s soul, which is fragmented after he sacrificed himself. So Bihwan’s brother put a fragment inside him. This is the reason that he constantly needs yin (or yang, idk anymore) energy because he doesn’t have a full soul.
On the other hand, Bihwan’s brother also either possessed geonryong (I think thats his name I keep forgetting) or convinced him to help (though from the way bihwan acts i assume the former), who is the dude that took in minchan in after the school disaster and after granny died, because he felt indebted to granny and maybe also just because he felt sorry for minchan.
We can for now assume that Bihwan’s brother is actually king jinmu, since bihwan comes from royal blood and it fits with the dream sequence where the two of them talk, which means he’s the one who is so fucking angry (probably because of seoho’s irreversible death and impossible reincarnation due to soul fragmentation) that he would rather watch the world burn than accept the situation. So he destroyed the paths between gods and humans (still dont get what thats supposed to help with but maybe well get an explanation later) and is currently targeting the samsin, presumably to get the other fragments of seoho’s soul.
For now, minchan wants to talk to geonryong and hear his side because he thinks of him as family. Why exactly that means he has to separate from bihwan, I don’t know.
Hope this clears some things up :)
But is granny dead? Doesn't he keep her locked up?
Well I mean, the current state of the plot is that she died. Could turn out differently later though I guess
But what was that scene where he looked into a shed or closed and she was there, he being like "oh were u asleep" at the end of chapter 8
The plot is so thick I got lost in it and now im confused