Samurai Spirits - Haoumaru Jigokuyuki

The story begins with Hanzo Hattori checking on his comatose son, Shinzo. Although he knows that his son's body is alive, Hanzo laments his powerlessness in saving his son's soul. While he prays for his son's revival, Shinzo's soul flickers into his body. He tells his father that Amakusa's soul is still alive in the Makai (demon world), begging his father to stop the villain. Moments later, his soul is struck back into the Makai by Amakusa, once again leaving Shinzo's body lifeless. Enraged and in grief, he leaves to try and get his son's soul back.

From Viz: The year is 1787, Tenmei Era, a time of plague and famine in Japan, When ordinary swordsman only add to the piles of corpses on the street. But Nakoruru, a nature-worshipping Ainu priestess; Haohmaru, a bold samurai with a death wish; Hanzo, a ninja loyal to the Shogun, are samurai spirits with a common destiny. With Nakoruru's guidance, the trio battle the supernatural forces of the Dark Kingdom, led by the half-human wizard Madou Shiranui. If Shiranui's troops succeed in fomenting a war between Japan's warlords, the resulting devastation will clear the way for Dark Kingdom invasion of earth. Can the the brave samurai stave off an all-out attack by an entire legion of demons?