The generals during the Warring State Period that passed away without unifying the country have waken from death as vengeful spirits and turned the world into a "Darkness Warring Country". Fighting the "Darkness Warring Country", underworld Uesugi had the most powerful "FORCE" and purified the bad spirits and sent the spirits to the underworld. A boy named Takaya Oogi is told by Naoe at one incident that he is actually Kagetora Uesugi, the head leader of Uesugi Underworld Army...

(Source: Aniplex)