In 2030, Japan. A virus has infected humans throughout the world. Infected people turn into different forms of monsters based on their ages, sexes and races. The virus is named 'Gibia' - after being rich in variety like gibia. Just then, a pair of samurai and ninja appeared in such a blighted wasteland of Japan. They both traveled from the early Edo period, fighting together with help from a doctor who tries to find cure for Gibia. Facing ceaseless attacks from Gibias, and outlaws that attack travelers for food, they start the dangerous journey with enemies all around. Source: Official website