The Land of Han'ei is a home to many. It is the Realm of Man. One if three realms. It was created by one of the three Great Gods, the Heavenly Divine Dragon. All was peaceful within Han'ei. Until...

One day, the Yo-Kai Kunshu, creator of the Realm of Spirits wanted to exterminate the Realm of Man. So she realeased a curse. Whenever a human died, their soul could transform into a Yo-Kai. A feral spirit with no memory of its humanity. That exists only driven by instinct.

The Yo-Kai caused immense bloodshed, killing many humans. Such bloodshed resulted in a major imbalance of souls that arrived in the Realm of the Damned, created by the Oni King. Thus the Oni King released his own curse, believing it was the Heavenly Divine Dragon's fault. Whenever a human has overwhelmingly evil desires, they will transform into an Oni.

Oni have special abilities unique to each one. They retain their human memories but gain a desire, one that can only be met once they perish. They are immortal beings. And they feast upon human flesh to grow strength.

Having witnessed the carnage, the Heavenly Divine Dragon needed a solution. So he found a human swordsman who was pure of heart. And that man would be blessed with the power to become the first Heavenly Swordsman.

2,000 years have passed since those days. Yo-Kai and Oni are still around however now exorcists exist that manage the Yo-Kai and swordsmen have developed techniques to fight with Oni.

Many eras have passed since then aswell. 27 to be exact. Each era named after the Heavenly Swordsman of that time period. And it is those tales that inspired many to strive for that goal. To be the Heavenly Swordsman. To have history named after their achievement.

One of such individuals, is a man named Kachito Mishimura. The hero of this story...