Why didn't Kimura Masahiko kill Rikidozan?

December 22, 1954. Kimura Masahiko, who had switched from professional judo to professional wrestling, faced off against the then-popular Rikidozan in the "Showa Ganryujima Showdown," a contest dubbed "Japan's Strongest Man." Though the match was pre-arranged to end in a draw, Kimura was utterly crushed and knocked out. While only two networks were broadcasting the event live, the viewership was 100%. Kimura, then 37 years old, was left in a pitiful state in front of the entire nation. This humiliating event occurred at the turning point of his life, as he lived to be 75. During his judo career, Kimura viewed judo as a martial art for the deadly fight. The night before each match, he would always practice seppuku (disembowelment) by placing the tip of a short sword against his abdomen. It was this determination to commit seppuku if he lost that led to his unwavering victory. Unable to forgive Rikidozan for breaking his promise, Kimura takes up the dagger he once used to practice seppuku and sets out to kill him. However, in reality, things don't go as planned... What lies beneath? This epic epic revolves around the "Battle of Ganryu Island," considered the greatest mystery in postwar sports history, and details the life of Kimura Masahiko, the greatest judoka of all time!