The cast of AoKen live in the far future, when Japan and California have become one: Rim. As such, people seem to hail from both cultures.
*Aobuki Izuki, the main character is a samurai in an age not needing samurai. He's broke and can't find work. At least, not until his younger sister hooks him up with a job working for...ninjas. Something's not right there. No one but Aobuki seems to notice though...
*Shoko Izuki, Aobuki's little sister and resident gunsmith. Unlike her brother, Shoko learned skills that would be beneficial and makes an honest living selling, making, and customizing guns.
*Furuichi, head of the Rim Shinobi Association, carries out requests and espionage missions with her two most trusted officers, *Mikomico Moka and *Rei Miyomi. She also hired Aobuki and has a crush on him.
*Sarabella Norizaki, a psychic who uses calligraphy to convey her predictions. She is well known throughout Rim for her accuracy.
Tojo Orihara, captain of Rim's head police force, usually seen accompanied by *Josuke Ginkame and *Joseph Saratoba.
*Priyanka, a traveler from the Land Beyond The Wall (what was once India), Priyanka traveled to Rim in search of her brother. She has a fondness for alcohol and hints at having feelings for Aobuki.
*Sanjay, Priyanka's brother and a military soldier, Sanjay hates having so much responsibility and usually gets out of it somehow. He even went full-on AWOL and hid in Rim for a while, before being discovered by his sister and colleague, *Anatolla.
*Viktor Toberelii, an assassin that went undercover for a while in Rim before taking out his target and leaving. During his time in Rim he got to know a young Shoko and even became her mentor. He returned in the current time to hunt down another target who looked a lot like Shoko, causing them to fight in a battle between student and master.
Also barely shown is *Naranja Nitana, the series villian who knew Aobuki in the past.