After the "prehistoric times", all things returned to equality. The surviving humans who could not withstand the large amount of radiation contained in the sun turned to live underground, while on the surface lived a humanoid race called Lunarn - the beautiful Lunarn with golden eyes were not afraid of the radiation in the sun, and their skin would emit soft fluorescence under the moon.
People soon noticed that the serum of the Huiyue tribe could extract antibodies that allowed them to safely expose themselves to sunlight. Humans initially tried to communicate with the Huiyue tribe, begging them to provide blood samples. After being rejected by the Huiyue tribe, driven by despair and greed, the profession of lunar hunter, which made a living by capturing Huiyue tribesmen, came into being. As the underground city-state grew, the functions of the Moon Hunters also tended to be diversified, eventually completely replacing the traditional army and becoming an indispensable armed machine for the city-state government.
In addition to the official moon hunters who are affiliated with city-states, there are also a small number of independent moon hunters who wander between city-states. Living such a life, Nate Adler wandered the desolate land between city-states, haunting the gloomy black market stores, until the lights of Siero City gave him a reason to stay...