Naraku Ninja

A mysterious ninja soul who possesses Kenji Fujikido. As Naraku's craving for massacring ninja overlaps with Fujikido's lust for revenge, together they bring Ninja Slayer—a terrifying ninja killing Grim Reaper—into existence. The more their mental resonance and physical symbiosis deepens, the more powerful Ninja Slayer's karate becomes. If Fujikido completely surrenders himself to Naraku, the strength of his karate will become nearly invincible.

(Source: Tokyo Otakumode)