The series is set in a world inhabited by four major races: humans, the powerful bird-like Rekon, the flame-wielding
Tokkebi, and the reptilian
Nhaga, who relinquish their hearts for immortality, allowing them to dominate the southern half of the world.
When a Nhaga envoy is dispatched to North, a trio—each member representing one of the remaining three races—is assembled to escort the envoy. However, the original envoy is brutally murdered, and his replacement is an anomaly: a Nhaga who still has a heart, making him much more vulnerable. As the rescue party navigates hostile terrain and centuries of animosity, they must confront their own prejudices and uncover the hidden purpose of their journey, which may determine the fate of the entire world