Hanachirutani Sanjinkou

This is a story of the past. One of the country's olden days, which, however, passed not that long ago... A period between the two great wars. At this time, electric lights are shining and buildings of steel and cement are standing in the cities. On the other side, at the very same time, virgin forests, where no human has set foot, remain, and in their dense shadows, legends and tales are hidden.

A young man pushes on through the dense blankets of the mountain air while stepping on thick piles of fallen leaves. Yes, the person who rushes through the gaps between the trees is an Asura. A demon who scorches his flesh in a blaze of vengeance. That young man, whose dearest girl was brutally murdered, is pursuing his enemies in the deep mountains, with his eyes desecrated with flames of revenge.

Nemeses, nemeses, abhorred nemeses.

Who are the sworn enemies he chases and intends to slaughter? They are the ones who nest deep in the mountains, where no one steps, fussing, and playing around... Are these men? Mountain monsters? These are sanjins. Those who are different from people living in towns and villages. Bizarre and distorted things.

This is the story of revenge.
The story of a young man whose beloved has been taken away, who runs around across the mountains, continuing his pursuit while dragging in not only his foes, but also everyone else around him, ultimately leading them all to their doom.

[Translated from the official site]