Decades after the fall of Japanese warlord Nobunaga Oda, Soki, a warrior who possesses Oni powers is on a quest to stop Hideyoshi Toyotomi, who has unified Japan in league with his demonic army of Genma.

It's been almost two decades since the fall of Japanese warlord Nobunaga Oda. The fallen ruler's own vassal Hideyoshi Toyotomi has succeeded in uniting Japan under the banner of peace... until June 29th, 1596 when a strange, glowing planet appears in the sky. From that moment on, Hideyoshi is transformed into a power-mad dictator and the country is rocked by natural disasters. Soon an evil army of demons appears; disorder spreads across the country; people are lost; and villages are burned to the ground. Just when it seems Japan is approaching its darkest hour, a mysterious warrior appears on the scene to try and stop the havoc. He's Soki, Oni of the Ash -- otherwise known as "The Blue Demon." The latest chapter in Japan's epic struggle between good and evil has begun.

The alternate costumes are Street Fighter characters.

In contrast to the first two games, Takeshi Kaneshiro does not voice his character in the Japanese version of the game.

Jubei Yagyu Akane is the niece of Jubei Yagyu from Onimusha 2 (2002).

First game to fully acknowledge the fact that Nobunaga is dead.

Tenkai is Samanosuke. Despite the fact that he is close to 100 years old, the Oni Gauntlet ages him at a slower pace.

Three characters from the first Onimusha are in this game. They are Hideyoshi, Fortinbras, & Samanosuke.