Three Forbidden Books: Eins

There are three major forces existing in the underworld: The Seven Emperors, Cross and Heavenly Demons.

Among them, Ains Milan, the Third of the Seven Emperors, headed towards the surface at the order of the First, Luna Farner.

The Demon-Gods once ruled the demon world... However, half of them were killed by the supreme commanders of the Cross and Seven Emperors and fled to the surface. Since then, in order to take revenge, they have been destroying a multitude of countries on the surface and accumulating power.

Ains travels to Uldra where Eins resides to investigate the spread of the Tenebris and encounters Rahd, the Black Demon-God who is attempting to use the Tenebris to gain power and extract the first of the Three Forbidden Books, -[EINS]-, out of the main character (also named Eins).

After holding back Rahd temporarily, Ains meets Eins and sends her to retrieve 3 items needed to contain the Tenebris, being the Sunstone, Experiment Data, and Magicite.