Returning to a devastated earth, humans use the Testament to help guide the path they must follow to go into space again. With only the islands of Japan habitable, the nations of the world are armed with the ultimate weapon: a Roysmoi Opro, an armor of deadly sins, and vie for power to protect the parts of Japan that they have claimed. But the Testament ends abruptly in its last year, implying the end of humanity. Tori Aoi and his fellow high school students from the aerial metropolitan ship Musashi decide to change the course of destiny, including the fate of a female cyborg who resembles Aoi's late childhood friend, Horizon.
