Quite some time had passed since the hunt had begun. The creature had finally come to realize that its life was truly at stake this time. Whoever this predator was, it was determined to hunt and eat it. Previously, its encounters with other predators had been brief, and it was able to disengage and escape. But not this time, this time it was truly in danger.
It abandoned all hope for outrunning and escaping its opponent on land, the human boy was too fast, and its flesh was too damaged and exposed to dig underground. It threw itself at the boy, hoping to take its life.
Rui on the other hand, felt much more pressured once this happened. It was much scarier to fight a beast that used every ounce of its mind and body dedicated solely killing you than it was to running away and fighting back in self-defense.
The two scenarios were on two different levels of difficulty, even if the latter was easy to handle, the former wasn't.