Nobunaga Oda began as a ruler in Owari before gaining supernatural power. His transformation into a demonic entity occurred when Ranmaru Mori, an extraterrestrial demon who arrived on Earth centuries prior, granted him control of the Oboro Host and the power of a "black demon god." This alliance fueled Nobunaga's supernatural campaign to conquer Japan.

As a demon warlord, he commanded monstrous legions, including a massive three-headed demon that destroyed entire villages. To eliminate threats, he orchestrated the annihilation of the Kasumi, Hyuga, and Hagakure ninja clans, specifically targeting the guardians of three sacred weapons prophesied to defeat him.

Nobunaga relied on the Oboro, seven demon ninjas with distinct supernatural abilities, to execute his campaigns. Key operatives included the lethal combatant Jinnai Saegusa, Masago the silk-spinner capable of causing instantaneous head explosions and body possession, and Kagami who reanimated corpses for assassinations and military operations.

Unbeknownst to Nobunaga, Ranmaru manipulated him throughout. Ranmaru had orchestrated the prophecy of the sacred weapons and provided them to the ninja clans centuries earlier, intending to use their combined power to open a gateway to the underworld. Nobunaga served as Ranmaru's unwitting puppet.

During the Honnō-ji Incident, Nobunaga evaded assassination using a body double; Ayame and Sakon killed the decoy, allowing the real Nobunaga to continue his reign. In the final confrontation, Ranmaru fully transformed Nobunaga into the "black demon god" to breach the underworld. Nobunaga was ultimately destroyed when Ayame, Sakon, and Ryoma united their sacred weapons—a short sword, a sword, and a spear—against him, nullifying Ranmaru's influence and ending his reign. Information about his physical appearance before demonic transformations or pre-Owari activities is absent.