The Gate of Nemesis. 

It is a protective barrier between the realm of mortals and another realm. 

Eons ago, a civilization known as "[i]Vancia[/i]", formed of Humanoid Dragons, prospered. Vancians were lovers of knowledge and always aimed for scientific and magical progress, banishing undesirables to a barren dimension, the "Realm of the Black Stone".

In order to prevent banned criminals from leaving the Realm, the Vancians set up the Gate of Nemesis as a means of sealing both dimensions and setting them apart.

Time passed, and the Vancian civilization came to pass. Humans were born, and a civilization of Humans named "Eden" prospered. Criminals banned to the Realm of Black Stone spent countless generations building up power from their existance, turning themselves into hideous monsters of many shapes, ranging from corrupted Vancians to Giants, and invaded Eden.

A war of centuries ensued, and only ended when the Sorceress Maya fused her body with the wind goddess Sylph, and sealed the Gate of Nemesis. After the war of Eden, several civilizations prospered in the realm of mortals, with the Realm of the Black Stone absorbing other realities and looking for a princess pure of heart, with an affinity for wind elemental magic to complete the process.

An alchemist, turned into a vampire while seeking for immortality, set his eyes on a beautiful noblewoman. He knows about the story of the Gate of Nemesis, and wants to use its power for his own goal, while the noblewoman herself is a girl, saddened by her harsh, rigorous lifestyle, and dreams of finding someone to be happy with.

All while a wanderer raised in a distant land, who's also a young master in the ways of the ninja, suddenly gets wrapped on this intrigue...