I got a theory regarding the mem loss-
Probably there was only one true hero. After his passing humans kept reviving the body with souls of otherworlders. That may explain so many hero bodies in his mind(?) When he eats. And the thing he was eating was himself in the jester fight. And every hero did so which is a system to make them forget themselves and become the hero of this world only.
Chances are low but would be nice if this comes true.