Across the galaxy there's a hellish planet where humans and tribes of demons are at war.

The strongest demons are Bloods, the Senketsu Oni, who are said to be conquering the planet.
The smartest demons are Creates, the Souzou Oni, who gain power by tactical wiles.
The largest demons are Titans, the Kyomi Oni, whose vitality derives from the planet.
There are the aimless Lost, a race of lesser demons without horns.
Finally, the struggling Humans.

Long ago the the humans hunted the oni and cursed them
so that only males were born. For this, the oni waged a terrible war.
The humans were at a disadvantage until hope arrived with Momo Hinogami.
She became known as the Cruel Sniper, an oni-killer that struck fear
into the hearts of demons.

But her legend is not a happy one. Momo couldn't save the humans.
The oni captured her, and will teach her true cruelty...

[From DLsite English]