we all knew how sick, manipulative,and obsess mujin is to choa. its just kinda sus that he let choa be alone with siran... for a long time that he was able to abuse him and he knew that siran hurt choa that night and yet he still let them be alone in the woods the nxt day hmmnn im guessing mujin is aware of everything got a fetish for it and a 3some in d future is coming hehe just a wild a guess! also the author allowed the rape to happen makes sense
they look like siblings to me haha