A brief description of the manga Rebuild World:
At the risk of his own life, the boy steps into the wasteland where people once lived. His name is Akira, and to get out of the slums he was born in, he became a hunter. In the wasteland, he meets a strange girl, totally naked.
Her beautiful body is ephemeral, you can’t touch her, and only he seems to see her. She calls herself Alpha, and with a bright smile gives her first assignment to hunter Akira.
Although it is not clear what her intentions are, Akira accepts her assignment and contracts with her to become stronger as a hunter. And from that moment on, their exciting hunting life began.