He didn't want him to see that he had actually cum despite being rapped?

no, the thing with rape victims is that society often stigmatizes rape and makes it look like the victims fault, so that leads to rape victims believing that they’re “dirty” and such WHICH IS NOT TRUE but basically hyesung feels that way and doesn’t want seungchan to see him. you can see it when he thinks, “only the good things” therefore, he only wants seungchan to see his good sides and panicked because the state he’s in right now is deemed as “dirty”

ohhhh, thank you for telling us