Seihin Of Hikari: Secret Lands Vol 1

In the Ryukyu Islands, people are prohibited from leaving the country. It's a place secluded from the rest of the world. However, Nagishima found himself in a government program due to the massive debt of his family. He undergoes training and is sent to an unfamiliar country named Atarashī Kōya, where he discovers its inhabitants are all of a peculiar race called Seihin. He is then tasked with fighting the rebels, mapping the region and documenting its people and resources.