Set in a post-apocalyptic version of Earth sometime near the end of the 20th century, a nuclear war has left the world in ruins, causing the oceans to evaporate and destroy most of the world's vegetation. Most of earth's survivors include villagers who try to thrive on what little resources they have and the numerous vicious gangs and tribes who prey on them. A martial artist named Kenshiro, a man with seven scars on his chest and the chosen successor of the legendary assassin's art Hokuto Shinken The Divine Fist of the North Star) has sworn to protect the weak and innocent from the malicious gangsters that threaten their survival. Accompanied by two young children named Bat and Lin, Ken confronts numerous violent gangs through his journey. Eventually Ken faces his adoptive brothers who were also trained in the art of Hokuto Shinken, as well as the six top masters of the Nanto Seiken ( The Sacred Fist of the South Star) school. His ultimate adversary is his eldest brother Raoh, a would-be world conqueror who broke the Hokuto Shinken law by refusing to give up the style.

Several years after Ken defeats Raoh, he returns to help his former sidekicks Bat and Lin, now leader of the Hokuto Army, to fight off against the tyranny of the Heavenly Emperor's Army led by the Acting Governor Jakoh. Not long after Jakoh's defeat, Lin is kidnapped and Ken is forced to travel to the Land of Shura to rescue her, a land of warriors ruled by Kaioh, who uses the style of Hokuto Ryūken , The North Star Lapis Lazuli Fist), a malicious counterpart to Ken's Hokuto Shinken. After defeating Kaioh and rescuing Lin, Ken wanders off into the desert, continuing his journey.