It was easy to distinguish between the energy of Aura and the Mana. The fundamental difference being their nature.
While Mana was the energy that was of soul that used the influence of the nature outside the body as well as inside, Aura only relied on the inner strength.
Aura was the energy of the body, the soul that couldn't produce mana sometimes with the intensive training of the person ended up using Aura, which was the secondary life force of the person as the driving force.
If a mana user's Magic was a mental or innate ability then, the aura was an acquired physical ability through training.
The shapeshifters were the ones who used Aura since their bodies were born with the congenial trait of shifting from human into an animal. Their Auras developed as they grew and that was why they were physically so strong.
The only thing that messed with the Aura users was the Mana users since they had contrasting attributes.
