What's the real reason for helping the mc?
He is obsessive, there's a mental disorder name for that but I forgot. And his object of Obsessiveness is that OG!FL, he is like a loyal dog that will do anything for the OG!FL. OG!FL said she don't want MC to get hurt or die, she is sick too actually, have mental disorder too, and she said she'll kill herself if MC died and asked that black haired dude to protect her. He blindly accept that task because OG!FL ask her, despite knowing that the MC (before she transmigrated) is actually have the same obsessiveness to him. In later chapter, she showed that she is not the same girl he used to know, she no longer attached to him, no longer obsessive over him. It makes him angry and have inner thoughts like "how the fuck you're not obsessive anymore? Why you can be cured and I can't? Why is it I still have this obsession? You should go back to be obsessive over me too." That's probably where he started to shifted more of his attention towards MC rather than OG!FL.
Ahhhh so he's crazy! Thus everyone is obsessed with MC, got it! (〜￣△￣)〜
I read the raw, but every male leads candidates are all crazy.....only the pink haired dude is the sane one. Even the korean comments are all support him to be the male lead. As much as it is interesting to have that black haired dude as the ML, he is an obsessive bastard that I was suprised knowing his real reason to help MC. Also, this kinda reminds me of "Inso's Law" but darker, I kinda like it but it's a bit stressing for me.