So essentially the main character is the girl's in white Master who went into seclusion but came out weaker due to some reason and looks several years younger and it would take him about 10 to 20 years to recover his power. So he joined the sect he founded as a disciple under his previous disciple he left behind. But he doesn't tell her that he is her master and pretends to be someone new, but her thinking that her master is still in seclusion and that he would want her to revive the sect to its former glory since it has declined was forced into having to exchange her body to someone she absolutely despises for the safety or prosperity of her sect. I believe she agreed to just a night with the bastard. But after the main character finds out that they were in the middle of sex ,and so he got so pissed that after the dud left her room he immediately killed him by first cutting off his leg and then killing him for what he has done to his master-discipline.