The characters aren't mutated warriors like that other fellow said (at least not in the original japanese version). These people are extremely gifted martial artists. Kenshirô, the main character, is a master assassin and the next in line to take over the Hokuto shin ken art. As Ken is chosen to be the master of the art by his teacher, his older school brothers (mainly the menacing Rao) are outraged by this and choose to violently leave the order, killing their teacher in the process. Keep in mind that only one master can be chosen and the rest of the students must either have their memories erased or their ken (fists) destroyed. Apparently the art is only meant for the best warrior and no internal struggle must persist. The character, Shin is a master of the Nanto sei ken (south fist or something like that). He is the first of four other nanto masters who will confront Ken.
Anywho, one can describe Kenshirô as a mix of Mad Max and Bruce Lee with a Road Warrior/kung fu/samurai flick backdrop. The series goes on as Ken battles his brothers, the nanto masters, and a bunch of other freaks with some flash backs here and there to help explain the story. The great thing about this series are the characters. They're not just evil dudes who kill kill and kill. Not only are they extremely colorful, they all have their reasons for their actions. You'll find that most of the major villains are regarded as heroes by the end.
Because this series is based on a comic book, you can expect to find some glitchy plot holes. But don't worry, the characters and the action are enough to make you forget about these plot holes.
