It is difficult to predict what will happen next. I think Woojin is more or less starting to change his attitude towards Wooyeon. If at the beginning of the story he took the opportunity and r@ped him, then after the last hypnosis, when Wooyeon was sick, he admitted that he felt disgusting. I can't say for sure, but I don't think he'll go back to hypnosis, at least not towards Woojeon. Maybe he will apply it on Junghwi. I've read different stories, in some of them the psycho characters do evil, lead a righteous lifestyle and do evil again. But there are also those who become more humane as the story progresses, I hope Woojin is that hero.
Disclaimer: I am aware that in real life his place is in a mental hospital, but this is a bl manga, where r@pists can turn into adequate people...