Die Story von "Onimusha" wird sich recht nah an der Spielevorlage orientieren. Neben Samanosuke Akechi wird man auch Nobunaga Oda und viele weitere bekannte Figuren aus den Spielen wiederfinden. Die Story dreht sich dabei um den klassischen Kampf Gut (Samanosuke) und Böse (Nobunaga).
Bei CS gibt es eine umfassende Storybeschreibung: [..] In feudal Japan, 1582, the warlord Nobunaga is ambushed by ninjas, led by the brave samurai Samanosuke. Trapped, Nobunaga commits seppuku, but two sinister sorcerers reanimate Nobunaga's corpse with a half-human insect larvae. The resurrected Nobunaga orders the capture of two very special women to fulfill his evil plans.
When Britta, the daughter of a Dutch merchant, is abducted on board a ship by seemingly invincible warriors, her tutor and confidant Jacob pursues her captors, vowing to rescue her at all costs. Meanwhile, the beautiful Princess Yuki is also kidnapped, this time by ninjas that reveal themselves, incredibly, to be part spider. In search of Yuki, Samanosuke joins forces with Jacob to vanquish their common foe. In the Cave of Elders, he receives a magical sword that will slay all within its reach—friend or foe—and learns of a sinister ceremony at Inabayama Castle intended to blot out the sun.
Performing a dangerous, stealthy invasion of the castle, Samanosuke and Jacob find the women they love dressed as Moon Princess and Daughter of the Sun, ready to be wed to and ravished by Nobunaga. Aided by their allies, the two warriors attack the insectoid hordes, but Samanosuke falls in battle, seemingly dead. In a mystical encounter, he is given the option to survive and fight—but it comes at a terrible cost... [..]
