The story takes place in Japan. The year is 2030 and Earth has been completely overrun by a viral disease named Gibia that turns infected people into various different monsters, based on their age, sex, and race. A samurai and a ninja from the early Edo period travel together through time and arrive in a ruined Japan to aid a professor working on a cure for the virus. Together, they fight countless Gibia monsters, outlaws, and other fierce foes on their journey to save mankind.

The second series, The Second Guest is similarly set with 25 stories, except this time the main victim is a woman who has just taken a taxi home from her best friend's wedding ceremony. (Source: AniDB)

The third series, The Last Train is set with 26 stories during a bizarre train ride that Gregory embarks upon. (Source: AniDB)

Six stories will be developed as an anthology with a new interpretation of Grimm's fairy tales, incorporating dark elements. (Source: MU, translated)