Based on the events in the life of legendary Korean martial artist Choi Bae-dal (Oyama Masutatsu). Or more precisely, the film is based largely on a famous cartoon series by Bang Hak-ki, featuring Choi Bae-dal (1922-1994), a real life figure who moved to Japan during the colonial period and established himself as a much-admired karate fighter by founding a new version of the martial arts form called “Kyokushin Karate.”

In 1934, the young Choi Bae-dal watches his farm servant, Bum-soo (Jeong Doo-hong), fighting in the market in Gimjae, Korea. Bae-dal admires Bum-soo and starts to learn the art of fighting. Seven years later, 18-year-old Bae-dal (Yang Dong-geun) smuggles himself to Japan to go to an aviation school but instead finds himself being forced into the Kamikaze program. He resists and fights with the Japanese instructor Kato, a karate master and captain of the program. Bae-dal is shamefully defeated and earns Kato’s scorn.

Humiliated and wasting away his time, Bae-dal meets Bum-soo again and is rejuvenated. Bum-soo gives him a copy of Miyamoto Mushashi’s Book of Five Rings and thus turns things around for Bae-dal. After Bae-dal meets Youko, a beautiful geisha with a pure soul and saves her from some cruel American soldiers he begins to wander the street at night saving women and others form bullies, robbers and worse. Youko starts to believe that he is the legendary vigilante hero Mouko and their tragic love begins.

One day Bum-soo is brutally killed by some yakuzas. Bae-dal goes to the mountain in grief. After a bout of incredibly intense self-training, Bae-dal searches throughout Japan hunting down the best martial arts masters to fight and conquer…