More than ten years have passed since the “Gate”, a passage connecting different dimensions and the current world, suddenly appeared. People called “Hunters” appeared in the world, and people who awakened extraordinary powers appeared.Hunters attack dungeons inside the gate to obtain rewards to make a living, but among the powerful hunters, Shun Mizuno lives as a low-level hunter who is called the weakest weapon of mankind.One day, after encountering a high-level double dungeon hidden in a low-level dungeon, Shun Mizuno was seriously injured and on the verge of death, and a mysterious mission window appeared in front of him.When death was imminent, Shun Mizuno decided to accept the mission and became the only one who could “ upgrade”——