Special Magic Core
So she had to take shortcut.
And this shortcut was developed by herself to strengthen her physique using mana and the formation inside her body. The moment she reached rank 4, part of the mana would be delivered by the formation around her heart to strengthen her other parts of the body too.
But because of this method, Riya's need of mana has become greater.
The amount of mana Riya needed in her advancement become several times more than other mages and magic warriors.
Magic warriors were the one who needed least mana among them all. They only needed to reach the very minimum of each mage's rank to advance to the next rank because their main focus was not their mana. Most of those who picked the magic warriors path chose this path because their mana's progression was too slow.
Of course, there were always some exception.
Some people were good at both physical arts and magic, so they picked this route that allowed them to use both.