Just my thoughts, if we have kept the girl as a guy instead, it would have been a really good Shounen-Ai. There are still aspects that you couldn't do because she is still a girl but it really helps with a few points especially since we are dealing with the Esports (since it is extremely male-dominated) scene.
I still like this, it is hilarious.
I don't usually read Messed-up BL, like Stalking Killing or Obey me, because I really don't view those as BL because we are dealing with some super taboo things that are super cringy and also becomes murder erotica material.
I really do like overall plot of The Beast Must Die, where in a sense we are dealing with a psychopathic character much like Dexter who decided that he wanted to kill in a sense of justice, in an attempt to appease his lust for killing. But we all need to realize that Kang Moo will never understand or feel romantic feelings for Kirin, only possessiveness and that's why I feel like this really isn't BL, we aren't getting a romantic ending, this will only end in tragedy. They are both fucked at this point.
Then I will have to question the fact that Kang Moo is actually a psychopath....
If you read it to the end, you'll probably understand Kangmu's psychology. If not, I'm sorry.
It's a story that's hard to sort out simply as not ending in tragedy.