I think he is starting to catch feeling for Mokyeon. I think he himself is not very aware of his feelings rn (we can see him feeling little off cause the twink knew Mokyeon hates seafood but Nanjo didn't and the bedroom scene, damn let's not talk about it cause it was awkward as hell lol) This is why he lied about being sick too and was mad at Mokyeon cause he thought they met each other and brought up the contract mid convo.
I think what is also interesting is Nanjo finding out twink and Mok had safe word which was never used = all twink did with Mok was voluntary and not forced from Mok as Nanjo originally thought? Also him finding out Mok doesnt eat seafood is interesting because I believe when Mok cooked for him, it was seafood, clams or something? So he picked it specifically for Nanjo even though he does not eat it himself. I also believe Nanjo is confused, it is just so weird that before he hasnt really spent time with twink, just gave him gifts and shit

At this point, the person I understand the least is Nanjo. I have no idea what he is doing, why, what is his goal. Zero clue.