what if Kaigaku changed into a demon earlier in the story when they were still training to become demon slayers. Cover goes to my friend Coffee

Summary: AU where Kim Dokja fakes his emotions and has been a heartless person since birth, aka he is a psychopath. He killed his dad and remembers it. It was an accident when the true mask on Kim Dokja's face started to crumble until it was no more than ashes, for that the Companions of Kim Dokja think it's not "him" because he was a calm and caring leader who would do anything to save other. Inspired by an ao3, I will credit them if I remember. Written by: JLMAA