The time is the Meiji era...
The event known as the Awakening has left the land in ruins.
With the course of history changed forever,
a new alternate history filled with evil spirits has begun to unfold.

Far to the north, large numbers of Oni have appeared and begin making their way south,
overtaking any villages that stand in their path.
A group of Slayers look to meet the Oni advance in Yokohama, defending the city in a fierce battle.

In the midst of the fighting,
a giant Oni appears in the sky and opens the gate that swallows in one of the Slayers.

Ten years later...
A lone Slayer with no memory of the past shows up in Mahoroba Village,
a small human encampment which lies far to the west...