A enormous underground labyrinth known as the "Tower" once was an enormous construct which towered over the earth, but it invoked the wrath of the Gods and was sunk deep into the depths of the earth. In the lowest level of this labyrinth, now used as a prison, a man has awakened. The man has no memories of who he is or why he is trapped in this prison. He now relies on a Black Blade he chanced upon and aims for the surface, he wanders the enormous confines of the Tower and relentlessly ascends. However the Tower hosts many dangers. Magical beasts which feast on the blood and flesh of humans, the towers' denizens who deceive and mislead strangers, and the dangerous beings of "Chaos" who stand in Velt's way. Chaos seeps into the minds and bodies of humans and leads them to ruin. Those corrupted by Chaos are no longer human. The most dangerous of the vile beings known as the Kin of Chaos is the "Demoness", the embodiment of lust, depravation and destruction. Velt's heart is constantly swayed by their sweet and seductive voices. Will the awakened Velt reach the world of the surface, a paradise of freedom touched by the sun's rays, or will he remain in the Hell of Lust, coloured by debauchery and hedonism. Velt continues his ascent within the darkness. [Translated from official website]