Tokyo, 2030. A pandemic called Gibiate, which transforms all regardless of age, sex, or race into monsters known as Gibier, has spread throughout the world. This is the age that the samurai, Kanzaki Sensui, and the shinobi, Sanad Kenroku, find themselves in after traveling through time from the Edo era to meet the Doctor and his assistant, Funada Kathleen. What future lies in store for Sensui and Kenroku as they face these monsters for the first time?

After meeting Kathleen, Sensui and Kenroku are invited into the camp where people have been living together. Kathleen challenges Sensui to a duel, hoping to learn how strong he is. Shortly afterward, the camp's lights suddenly go dark and the Gibier attack. Can Sensui and Kenroku fight against these unknown Gibier?

Sensui and the others decide to set out for a new location. Along the way they encounter a type of Gibier they have never faced before. Yet during that challenge a third man who has traveled through time like Sensui and Kenroku appears before them!