So my theory is that after his death, the book ML was sent over to the real world to become the bestfriend (either for a little while or maybe he was the book ML all along)
ML isekaied into the real world, lived a life there with that world’s MC and thought being happy together was easier. Then both he and MC get sent to the book world but now he can change the past but he doesn’t know this MC is the one from the real world. He thinks it’s his original love so he’s acting accordingly. So the ML is both a regressor and the best friend.
So my theory is that after his death, the book ML was sent over to the real world to become the bestfriend (either for a little while or maybe he was the book ML all along)
ML isekaied into the real world, lived a life there with that world’s MC and thought being happy together was easier. Then both he and MC get sent to the book world but now he can change the past but he doesn’t know this MC is the one from the real world. He thinks it’s his original love so he’s acting accordingly. So the ML is both a regressor and the best friend.
MC has only been isekaied.