Clearing a gate.

It was a rule established only after countless long and painful debates.

In the past—before the theory of gates had been solidified—there was a time when Hunters actively sought complete extermination within them.

But now it was known that monsters took a considerable amount of time to regenerate inside gates. And given their high reproduction rate, the industry had settled on an unspoken rule:

Leave behind about 30% of the monsters, clear the gate, and come back later.

That way, Hunters could maintain a steady income and continue to harvest magic stones in future runs.

Magic stones had become an indispensable resource in society.