Could it be that they couldn't cultivate the Purple Demon Eyes because their bloodline tier is too low?  And Du Bai can do it with the Celestial Fox Vision's higher tier? It would make sense….4

This was a distinct possibility, and also a pretty favorable situation. If the Purple Demon Eyes could help Du Bai continuously enhance his spiritual power, and considering that Tang San confirmed that the Celestial Fox Transformation was able to devour spiritual power to improve, then it was actually possible for Du Bai to use this method to break through.1

After breakfast, the group couldn't stay put. Wu Bingji and Tang San were aware that the mayor was following them secretly. They set off again, heading deeper into the jungle.0

According to the map, they had about a day's journey...0