In the end, it all depended on the person how he used the magic.
As Saito continued to run fast, he suddenly stopped running as he sensed a weak magic signature.
Even though Iris hadn't spoken anything, he felt like he was going in the right direction. His magic sense had been enhanced a lot after the Golden Dragon's Bloodline and the purification from the Spring Water. It perhaps even exceeded the range of Iris.
Suddenly, when he was around 50 miles away from that Magic Signature. He heard Iris speaking up.
[Master, continue to move towards the same direction and you shall encounter the Illusion Formation after 20 miles.]
[19 miles…]
Soon enough, it seemed as if a countdown had started while he continued to run with an excited expression.
After Iris' count reached 0. Saito suddenly stopped and spoke out in his head 'How far is this Illusion Formation from me right now?'