Hashiba Takeru is the leader of Global Operation Service (GOS), a secret spy organisation housed within the Public Security Investigation Bureau which is tasked with eradicating criminals who are targeting Japan for various reasons.
Many years ago, a Great Civil War ravaged Japan, leaving the country fragmented between two regions: Kansai and Kanto. In Kansai, a group of six Akudama carry out missions given to them by a mysterious black cat, while evading the police. But a dangerous journey is about to unfold when a civilian girl becomes twisted into the Akudama's way of life and witnesses their criminal drives.
Nikita is a drug-addicted juvenile delinquent who was accused of killing a police officer in cold blood during an attempted robbery of a pharmacy. She is later arrested and sentenced to death by lethal injection, upon which she was secretly drugged by the government, faking her death. Nikita is then "recruited" by a secret government organization and transformed into a highly skilled assassin who cannot be traced.
David Jung, a mysterious former US intelligence operative living in hiding in South Korea, has his life blown to pieces when the consequences of an impossible decision from his past come back to haunt him, and he finds himself hunted by Rebecca, a deadly young assassin, and Caddis, the sinister spy organization she works for.
The Meiji Era was one of great renewal for Japan, where swords and killing were outlawed. However, many survivors from the time of Revolution still live, lurking in the shadows and waiting for a chance to use their killing blades again. Only Kenshin Himura, formerly one of the most brutal of killers, hopes to keep his swordsman's honor and still live in the new era.