Soul represents body
From his knowledge of these, the soul was the representation of the body.
If his soul is unaffected by these worlds, then his body is also unaffected because he was reborn here, and the soul constructed his body.
Although he didn't have any soul magic book, still, his comprehension allowed him to at least comprehend this much.
"I knew upgrading the life level was definitely the best option for me." Aur thought.
The body could still be upgraded by various means, but the soul was increasingly difficult to increase because they were very rare in the world.
He had tried to ask Asmodeus about it, however, this old monster always kept his mouth shut.
"Forget it, I will quickly comprehend these spells, although it might not help me because of my lower tier wizard realm, but I can still gain some reference. These Sword intent spells are interesting." Aur mumbled while comprehending the spell.