asuya

Roy died during a war against the Evil God Cult, but somehow, he returned back in time to 30 years in the past where he was just a boy who awaken his summoning magic. 
Just a few days before his death, he became the only Aura user in a world of magic. 
Using his knowledge and experience, he will become an Aura user again, faster than his previous life. 
Accompanied with a shape-shifting black slime, he will make sure to protect everyone he cares about and win against the Evil God Cult.

The Only Aura User In Magic World

If he was trained to be an Aura user, and he somehow knew that the other people who trained with him died for some reason, then he should have known that their boss, the Evil God, was killing those who were successful in becoming Aura users.

One is that the mage in front of me is also an Aura user. But I doubt that. He just trained diligently so he became stronger than master level mages in his physical strength and magic. But the chance of him being an Aura user is not zero.

The other answer is that he's unable to become one no matter what.

I was an idiot. So when I thought that I will become stronger just by training in my past life, I never thought of any other things. I even saw how stupid I was in training when I saw the recording of my past life that the Spirit King projected.

Aerial Battle