The decline of the once robust fields of science and technology led to a new energy source for the modern era: magic. Humanity creates Gears, forbidden biological weapons. Those same Gears eventually stand against humanity in rebellion. Although they managed to overcome the war for survival known as The Crusades, humanity's losses were so great that even after several decades, their emotional wounds remain raw.
Sin Kiske, the child of a human and a Gear, heads to the wedding ceremony of his father Ky and his mother Dizzy. Their wedding breaks the ultimate taboo of a union between human and Gear. Even with the world at peace, it took many years before such a ceremony could come to fruition. Despite the complex array of emotions surrounding it, the wedding is met with blessings.
When suddenly, a mysterious girl appears...
The fated child inheriting the blood of Gears. The mysterious girl who despises Gears. Their meeting will shake the world.