End of Edo Era - It was the last time a man lived as a samurai and fought entrusting his life and briefs to a sword.

It was the time when long peaceful Tokugawa Dynasty began to be overshadowed triggered by the arrival of Westerners. During the upheaval, when youths were seeking for new age, there was an existence that brought turmoil and chaos. It was called Hasha no Kubi, or the Head of Conqueror. It was said that the person who could obtain the head awoke in revolution time could rule over the whole country. On the other hand, there was another shadow existence called Eternal Assassin. They have been destined to fight Hasha no Kubi in order to seal. Both had been fighting each other behind the history. Their fights have affected the history involving those who wanted the power.

Someone wanted it for themselves, someone wanted it for avenges, and someone wanted it for their ideal...

Their thoughts cross each other over the Hasha no Kubi. Their thoughts put tougher as if they were complicated gear wheels. Then, it began to move the history as if it became an engine that moved to the future...