If players were to battle monsters, it would not be an easy task. If they fight for too long, not only do their weapons and equipment need periodic repair, but once their medicine is exhausted, they absolutely have to return to an NPC city for a refill. However, NPC cities are not found everywhere. For monster-hunting spots not far from an NPC city, it's relatively manageable, but for some areas, a round trip can take a rather considerable amount of time. This greatly impacts the efficiency of the players' monster hunting. Consequently, no one knows out of what considerations, but after paying horrendous costs, the NPCs specifically made arrangements for such situations.