The plot 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, 11-year-old Bae-dal (Yang Dong-geun) watches his father`s farmhand, Bum-soo, fighting with Japanese officials in the market in Gimjae, Korea. He admires Bum-soo`s fighting skills and starts to learn to fight.
Seven years later, 18-year-old Bae-dal smuggles himself into Japan to enroll in an aviation school but instead finds himself being forced into the Kamikaze program. He resists and fights with the Japanese instructor, Kato, who is a karate master and captain of the program.
Bae-dal is shamefully defeated and earns Kato`s scorn. His pride deeply hurt, he determines to get stronger and learn real fighting skills. He happens to meet Bum-soo again and obtains a copy of Musashi Miyamoto`s "Book of Five Rings," a book detailing techniques on how to fight and survive.
The encounter with Bum-soo is a turning point for Bae-dal. He begins to wander the streets at night, saving women and others from bullies and robbers. A romance is inserted into the plot when Bum-soo rescues Youko (Aya Hirayama), a beautiful geisha, from some ill-mannered American soldiers.
However, Bae-dal can`t become complacent. His master, Bum-soo, is brutally killed by a Japanese mob. Filled with anger and desire for revenge, Bae-dal goes to the mountains and commits himself to intense self-training.
Now, all the factors are in place for a series of fight scenes as Bae-dal finishes his training and embarks on a journey to fight and defeat top martial arts masters across Japan.
