After narrowly escaping death, Kei Nagai and his newfound ally Kou Nakano seek vengeance against Satou, a fellow Ajin determined to conquer the world. As Satou carries out a series of brutal executions, humanity scrambles to find a way to defeat this immortal threat. Kei forms an unlikely alliance with former foes: government official Yuu Tosaki, who possesses valuable knowledge about Ajin, and Tosaki's Ajin assistant Izumi Shimomura. With a growing coalition at his side, Kei races against the clock to halt Satou's destructive campaign before civilization faces annihilation.