After a global-scale nuclear warfare has turned most of the world into a contaminated wasteland, with Earth's survivors now fighting over the few uncontaminated food and water supplies still remaining. Kenshiro, a master of the deadly martial art ''Hokuto Shinken'', is traveling with his fiancee Yuria when they are confronted by a gang led by Ken's former friend Shin, a master of the rival ''Nanto Seiken'' style. Shin proclaims that he has been in love with Yuria for a long time and with no law to intervene now, challenges Ken over her. After defeating Ken in combat, Shin engraves seven wounds on Ken's chest and leaves him for dead, taking Yuria with him. Ken's eldest brother-in-training Raoh, having witnessed the fight without intervening, returns to his dojo, where he finds his sensei Ryuken meditating. Raoh challenges Ryuken's decision to choose Ken as the ''Hokuto Shinken'' successor over him and kills him, proclaiming he will become the ruler of the new world.