
LOL
But the real question is, is he always thinking about fucking Nam? Like, how can he focus on other things (i.e. work, 'non-sexual thoughts?')?

Ronfl
Incredibly active, indeed...

He was thinking about doing him even when the director was speaking to them ._.. That guy has an incredible self-control.

I'm suspecting that he's an idiot to the point of obliviousness. In one of the first chapter, I think the second, he's talking about himself and his life. When speaking about Nam, he doesn't say that he loves him, but that he finds him entertaining. Why? He already admitted some not so nice details about his life, so I don't see why hiding the fact that he's utterly obsessed with Nam. Unless, of course, Ma hasn't realised yet what are his real feelings for Nam.

He realizes it in a way, in later chapters we see flashbacks of their highschool days when Sangtae was completely smitten with Jinwoo. The whole obsession thing starts as a "notice me sempai" scenario...
It would be embarassing to admit he's been hopelessly doing everything to be this straight man's number one preoccupation. He's fine admitting how crazy he is but might not want to come off as lame.
More spoilers (beware): as soon as he learns about the fantasy sharing, he gropes Jinwoo fondly, which is more a sign of lust than mere teasing. Then he swings between molesting Jinwoo and acting sincerely apologetic depending on his mood / Jinwoo's reactions.
I think he knows it's love, a messed up "I love you most when you cringe" thing.

That's an interesting explanation. I had never thought it that way, I mean that he might be fine with admitting to being insane, but not a man who's head over heels over a straight guy who despises him. It totally makes sense. That must hurt his ego and yeah, also his feelings.
I took a look at the raws and I have to say that Ma is definitely trying to make the best out of this situation *face palm*. Do you think they had sex in chap. 10 and 12? It seemed so, but I'm not entirely sure.
Bless the man's imagination.