I'm guessing nanjo has a saviour complex and him saving sunhwa from his "abusive" sexual relationship with mok gave him satisfaction.
Ppl are theorizing that sunhwa was mad because he has feeling for mok? Tho I don't think that's true. I think sunhwas ego was hurt and he felt humiliated to be played by mok and nanjo
i think Sunhwa was mad because he was fooled by them, they both went at it behind his back, this is betrayal even if he has no feeling for either Mokyeon and Nanjo this is just the way they did that is so shady and disrespectful.
To this day i don't think Sunhwa has any idea about the blackmail thing and such, he's just upset they played him like a fool, especially Mokyeon since he's his close friend - that's double faced(*). But then he was ready to forgive him when Mokyeon went to his house, but when he realised it was not to apologise but to get a hold of Nanjo through him it was the cherry on the cake.
Sunhwa also mentioned it was not the first time it happened(?). Maybe another "leftover" story from school days?
Sunhwa is having a friendship heartbreak rn - he lost his bff
They not only were fuckbuddies but also close friends who shared the same secret
wait im kinda confused why did nanjo like sunhwa so much?? and why was sunhwa so mad too i dont understand. also wow chapter 36 gave me ptsd to some dark times bruh