Onimaru is a ninja from the Iga village. Both he and his sister, Oboro, possess the blood of the Oni due to their mother's Oni heritage. His parents died when he and sister were still infants. Right before her death, Onimaru's mother brought both he and his sister along with an Oni Gauntlet to Iga village. She was found by legendary Iga ninja, Sandayu Momochi and with her dying breath, told him that she was a descendant of the Oni Clan. Sandayu then raised and trained Onimaru and his sister in the ways of the Iga ninja.
Shock is a skill that has an area of effect of one tile outwards from the target (can hit up to five targets). This skill does have uses early in the game though later on, it becomes too weak to be effective. His other skill, Frenzy Slice is a very powerful attack that hits an enemy six times. It has a high SP cost, which means it should only be used sparingly.
Later in the game, Onimaru acquires the Onimusha Attack skill, which allows Onimaru to transform into his Oni form. In this state, Onimaru becomes significantly stronger but does not gain experience. You also lose complete control over Onimaru until he reverts back to his normal form a few turns later. No matter what, this ability always costs 1/2 of his total SP.
- Onimaru is a drop item in Onimusha: Dawn of Dreams by the wielder of Jubei Akane Yagyu.
- Unlike Samanosuke's and Jacques Oni gauntlets, Onimaru's gauntlet is on both of his arms. Onimaru's gauntlets lack the trademark "eye" of typical Oni gauntlets.