The end of the Edo era marked the last time men would live as samurai and fight entrusting their lives and beliefs to the sword. The peace of the Tokugawa Shogunate begins to crumble with the arrival of Western influence. Amidst this upheaval, the youth of the nation seek a new era, but something else will bring turmoil and chaos. It is called Hasha no Kubi; the Head of the Conqueror. It is said that he who can obtain the Head shall rule over the whole country. However, another shadow being called "Eternal Assassin" is destined to oppose Hasha no Kubi. These two beings have been in eternal conflict, affecting the course of history from the shadows, influencing those who craved power. Some want it for their own, some want it for revenge, and some want it to fulfill their own ideals…
The wills of men intersect over the Hasha no Kubi. They combine and move together like complicated gear wheels of an engine pushing events towards the future.