ExSoldierLv99
Even without the time dilation, by the time he is powerful enough to return he would probably be too powerful to return (since powerful beings can't enter lower tiered worlds). His only hope is basically for Earth to have increased in tier while he was away to keep pace with his own growth and to keep them in the same time era. In any case, I'm amazed that he doesn't travel more either by going through dungeons or by transfer. Staying in the same place levelling up, was never really a great strategy