This is what i found on the comments and it explains a lot (belongs to user @Mih)
"The real world is what happened in the book. All that shit happened for real. Then MC dies and his dying wish is that he has a happy life. Then he and ML are dragged to this alternate world “created” by de MC where there’s no ABO and they are friends. ML remembers everything and regrets what he has done to MC, so he plays the royal friend, but writes a book about their past life, since MC doesn’t remember anything.
So after reading the book, BANG they are back in the real world, but in the past, when they first met. MC remembers only his alternate happy life and what he has read in the book, and ML forgot everything, and only remembers after they have sex for the first time. So MC thinks he’s in a book, but he’s in his real life and there’s no world to go back to actually."
it is real world that it left a big trauma on huimin, later on the side story where iheon had to go to another country to do business trip, he panicked that the world gonna poofed off (because that happened on their fabricated second life when iheon said he had to go to the u.s. and after that huimin got dragged on so he thought the "book" life which is their 3rd life)
someone please enlighten me.. did the iheon in the real world came into the book too OR did the iheon in the book intentionally bring the real life huimin into the story bc he harmed the book world huimin and probably caused his de@th?.. am i missing something or do we have so many things to be enlightend