After a global-scale nuclear war, the majority of earth's surface has become a wasteland, with most of the world's survivors fighting over the few uncontaminated food and water supplies. Kenshiro, the master of the deadly martial art Hokuto Shinken, is traveling with his fiancee Yuria (Julia in English version) when they are confronted by Ken's former friend Shin of the Nanto Seiken. After defeating Ken in combat, Shin engraves seven stab wounds on Ken's chest and leaves him for dead, taking Yuria with him. Ken's eldest brother Raoh, having witnessed the fight without intervening, returns to his dojo and challenges his Master Ryuken's decision to choose Ken as his successor over him. Raoh kills Ryuken and proclaims he will become the ruler of the new world. A year passes and Ken is found wandering in the desert. He rescues a couple of young children named Bat and Lin from bandits. Afterwards he allies himself with another martial artist named Rei, a Nanto Seiken master who is searching for his sister Airi. Ken learns from Rei that his brother Jagi has been impersonating him in an attempt to tarnish his reputation and draw him out. Ken heads to Jagi's lair and defeats him. Before dying, Jagi reveals that he was one who convinced Shin to betray Ken and that he is now living with Yuria in his stronghold of Southern Cross. Elsewhere, Raoh has amassed a huge army, expanding his domain by defeating rival warlords and begins heading to Southern Cross. There Yuria is treated with a life of luxury, living under the rule of King Shin. However, Yuria refuses Shin's gifts of affection, longing to be reunited with Ken. When she overhears that Ken is still alive, she attempts to sneak out of the castle, only to be taken captive by Raoh, who challenges Shin to combat. A while later, Kenshiro arrives at Southern Cross, finding the city in flames and Shin's men dead. Shin is still alive and fights Ken, but the battle does not last long, as Shin was graveley wounded in his batt

Kenshiro meets a blind martial artist rebelling against Souther named Shu, who is also one of the Six Sacred Fists.

While saving a group of children slaves from Souther's troops, Ken remembers that he once fought Shu in the past, back when he was still a child.