Responses
Well personally I think that the reason he commits the murders is because he wants the detective to be occupied by him, even though The detective doesn't know it. He wants the detective to only think about him and chase him, and he doesn't want to be left behind.
Oh, so he's fucked up to that extend (￣∇￣")
Honestly, I don't understand Seolwoo's motive on murdering people in gruesome ways. I mean he love the detective, so why separate himself from him? And we could see that the detective is so obsessed with Seolwoo that he is blinded ┑(￣Д ￣)┍ Let my ship sail safely ┗( T﹏T )┛