Tokyo Butei High School is a special school where armed detectives—"Butei"—are trained to use weapons. Kinji Tōyama is a second year student who has a special ability, but he keeps it a secret to maintain an ordinary, peaceful life. However, when he gets caught in a bombing on the way to school, he encounters Aria H. Kanzaki, the most powerful S-Rank Butei student in Assault Studies.
In the near future, Tokyo was left flattened as a result from a great earthquake. A new city, MegaTokyo, was then recreated due in no small part from the aid of a multi-million dollar company, Genom Corp. Genom created and mass-produced biomechanical creatures called Boomers to aid in the restoration of MegaTokyo. When the Boomers began to run out of control, the ADPolice at first tried to stop them, but they proved to be far more difficult to deal with than was first imagined. Under the ever looming Boomer threat, a group of four girls from varying degrees of society banded together. Calling themselves The Knight Sabers, they were the only ones with enough firepower and resourcefullness to defend the fledgling MegaTokyo from Genom and its berserk Boomers.
Spike Spiegel, a bounty Hunter with a dark past, lives on bounty to bounty, barely making it each time, or not making it at all. His partners Jet Black, Faye Valentine, Ed and Ein the dog all help him in his adventures from planet to planet.
Five girls live in 19th century London, a city within the Albion Kingdom divided into east and west by a large wall. The girls serve as undercover spies enrolled as students at the prestigious Queen's Mayfair school. The girls make use of their individual abilities to remain active in the underground world of disguise, espionage, infiltration, and car chases.