Four years ago, a large scale disaster in Tokyo claimed two million lives. The remaining thirteen districts of the city were isolated into the Tokyo Barricade Zone. Morisaki Harumi, an unruly kid with great fighting strength, is his family's sole survivor from the incident. One day, in a traffic accident, Haru gets pulled into a world of violence and meets Mana, the girl who turned herself into an ancient sword.

The manga takes place in a world where everyday life has suddenly crumbled away. In front of a young girl who is only waiting for death in this ruined world, a lone young man descends from an empty sky.

Sawyer is a cleaner who takes on the task of disposing of unwanted people in Roanapur, a city of vice where the mafia and other scoundrels thrive. Her daily life is depicted in a funny, sometimes horror-filled, sometimes action-packed, and even fantastical way as she goes about her work with her beloved chainsaw in hand. Her good friends and fellow freelancers Shenhua and Lotton, as well as familiar characters from the main story, such as Revy and Rock, also make appearances!