Responses

There was one panel that partially showed his neck, and I couldn't see a bruise, but as you said, Seungho could've seen this from his perspective and back off. We can all speculate whether it was a visible bruise or a change in his behavior towards Nakyum, all in all, let's hope for the best in the next chapter, god knows Nakyum needs it :')
So far I can understand both of the characters, Seungho may be pissed because after he confessed and made love to Nakyum, the latter just disappeared, in his eyes, it looked like Nakyum was waiting for a chance (Seungho being sick and tired out after sex) to run away, from the panels I couldn't see any marks on Nakyum's neck, but it may bruise more as time passes. Hopefully, Nakyum will confess and not try to empathize with the guy that caused all of this, because, after everything that happened, Seungho may believe his words for a change :')