I think that's the way its heading, I think...... Actually I hope.......
ACTUALLY YOU KNOW WHAT i DO THINK THATS WHERE IT IS HEADING
The way I see it, he is opening up to NK: needing NK's presence to sleep and calm his demons, and therefore allowing him to see him in a very vulnerable state (when he had the nightmare). Letting NK be privy of a very private conversation with is brother; again being vulnerable (clenching his fist)... He just hasn't told him YET about his past.
Somewhere deep inside, I'm just hoping Seungho starts to feel deeply about Na-kyum and find comfort with him.. to the point where he begins opening up his troubles and shit I guess I can only hope for this to be an enemies to lovers story