
So I think Nanjo is a closeted gay and was, like in many other stories before, pressured (by his family perhaps) to live the modest straight business man life.
I think that's also why rough sex is a no go for him, as he probably didn't have much of it prior to meeting Seonwha (sorry, if I butcher the name. I'm horrible with them) Also, might be a reason because he is extremely considerate in bed. Seems to me he is treating his bed partner like a delicate woman.
In regards to his relationship with Seonwha, we do not see much interaction apart from boring sex and Seonwha treating Nanjo like a cash cow. Maybe Seonwha is just his little rebellion or more of a tool to rebel against the life he was pressured into. For me there aren't really deep feelings of sympathy between them involved.
In the latest chapter it seems that Nanjo (despite being blackmailed into this situation) is starting to come to terms with his homosexuality. At least we can see an emotional development towards himself and the MC.
..MC, get a new identity, buy five flight tickets under your old name, board only one plane and from that destination take another trip under your new name to a safe place.
Just get away from these constantly horny f*ckers. ,