Well as I just read this, I can tell you. Isabel is married to the head of this "millenial" company and is trying to take over it. She is now acting as a stepmother for Shin, who is the only son of that CEO and also the only heir of that company. So Isabel wants to kill Shin but cannot before she can get to know what was his "mother's secret" (they still haven't told much about this secret). And it seems that Shin must also give up rights to inherit the company so Isabel could control it. Isabel has already killed Shin's real birthmother with her abilities and is trying to do the same for Shin. Cheese on the other hand is protecting Shin so Isabel is trying to get rid of him first and that's why Shin is now taking action against his stepmother, even though Isabel was blackmailing him with his father's life to not tell anyone.
As for the other man in the beginning, there isn't much info about him, but yes it would seem that he is inside Cheese (or is Cheese) and he was seen come out during the fight against Isabel (she controlled another person during this fight so basically it wasn't Cheese vs Isabel but "Cheese" vs Shin's boss)
This was a bit long but I hope it made you remember who she is. :D
Um wasn't that explained in the latest chapter? The reason Cheese has a red mark is because the 'second personality' is hanging on to his exostence.
*existence.
Your explanation was great! Now I remembered. Thank you so much! ♡
Honestly it seems more to me as if he's supposed to have been reincarnated and that happens to be his older self that refuses to leave his new self/personality with all the power as he's trying to make sure they actually succeed this time around, after all how would he know most of the things he knows I'd he were just some weird inner multiple personality thing with no different memory set from a time past?
It's been quite some time since I've read this so can someone please refresh my memory? Who was this Isabel and what was her relation to Shin and Cheese? And did Cheese have a second personality in him or who was that man in the beginning? It looks like I've forgotten the most important things, man, I'm dumb.