The story of the film is that in August 1945, as the US military was about to attack the Japanese mainland, the I-77 submarine was ordered to attack as the final line of defense. Captain Kuramoto (played by Hiroshi Tamaki) refused to use the human torpedo "Kaiten" (a suicide torpedo operated by a human), and had sunk several enemy ships with only ordinary torpedoes, which frightened the US military. However, his friend Captain Arisawa (played by Yoshikuni Dojin)'s submarine was sunk by the battle-hardened warrior, Captain Stewart's destroyer "Percival". Kuramoto was extremely sad and angry, and rushed to the final battle. In his heart, there is a score, which embodies the blessings of Arisawa's sister Shizuko...