imagine the demon lord somehow was limon I another universe or timeline lol

You know I was actually thinking that while reading this chapter.

Maybe Limon from the original story? (I remember them being in an ABO fanfiction of an original story, or am I confusing this with something else?)

No, you are right. The mc only know the original work, that's if I'm not mistake is a game, but the point is that's world mc is now is a ABO fanfiction