Rhod served the High Human's king Hélias III as a Pacted soldier, a slave whose loyalty is forced and emotions neutralised. After rescuing the prince Hélias IV from a transport-gate abduction, he himself gets stuck on the other side.

As he struggles to find a way back home, in a similar yet different place from his country, he discovers that the High Human's blood is the most researched material in here.

A race against time starts to save an unknown woman, known as "the last high human".