seongju (or whatever his name is, I'm just going to call him MC uke.)
MC uke's rude cousin who is very mean to his step brother is actually in love with him. the night MC uke was getting raped by the ghost, we see that his cousin was crying in bed.
the reason for his crying is what we see in 10th chapter. he was crying bcoz he caught his step brother doing a ritual or black magic thingy which will kill his whole family. He got a pot from the servants and it was filled with blood and a headless animal body. that's what the rude cousin saw. i think in the next chapter he will try to attempt suicide (it's not a spoiler, it's my guess). he will try it bcoz if his step brother doesn't love him and actually hates him so kuch that he wants to kill him, then he'd rather die quickly.
Can someone explain what's happening in chapter 10(no spoilers) I really don't understand