I think the reason why he (Yoonwoo) said 'Ngh' is because Taegyom cûmm3d in his hole a lot of times and in the next chapter (first panel) you can see the cûm seeping out of his hole if you look down below at his (Yoonwoo) b**/bu**.dazz it
I can't believe I dropped this Now I'm so glad I read it back, I'm so happy for them!!!!! I hope I get to see their side stories, this is making me cry