From what I understand the "novel" is their 1st life then mc dies and ml goes back to the past to change their fate, while mc has forgotten their 1st life and thought of it as just a story in a novel as a coping mechanism from all the traumatic shi he had experienced. When mc thinks he transmigrated into the novel, its actually him going back into the past with only his memories till he was 21(?) because of the trauma?