The present--A town on the coast in the rain. Kuramoto Izumi (Kitagawa Keiko) is about to see someone. In her hand she holds a letter written in English. The letter, sent from America, goes: ‘What did my grandfather lose that summer? What did he gain? Wishing to find out, I am writing this letter.’ The writer’s grandfather fought against the Japanese as the captain of an American destroyer, and boasted a glittering war record. Once it ended, however, he never spoke of his memories of the war, and left none of his belongings from that time. But among the things that he did leave was one that he had kept very carefully. This was a sheet of music folded into an envelope. With the yellowed, hand-written notes is the signature of Izumi’s grandmother, Arisawa Shizuko (also Kitagawa Keiko). To unravel this mystery of the past, Izumi has come to see Suzuki, the only person still alive to know her grandfather, who served as a submarine commander in the former Japanese Imperial Navy. Meeting the elderly Suzuki at an observation point looking out over the sea, she poses this question: ‘Japan and the United States were at war...that means it was a fight to the death, wasn’t it. So then why would he give this music into the hands of an enemy...why was it put away so carefully for more than 60 years?’ ‘There’s nothing hard to understand about it.’ Having said this, Suzuki, as if in answer to her question, begins to tell her his memories of the distant past. ‘We were all doing our very best...that’s all. It was a very long time ago. But that summer, those two weeks I spent with Lieutenant-Commander Kuramoto, I’ve never forgotten them.’ To the sea spreading out through the rain under Izumi’s eyes comes a summer 64 years before. The dark blue expanse of ocean begins to widen into August, 1945. The final days of World War II--the ocean southeast of Okinawa--off the Bungo Channel The Japanese Navy has deployed the I-77 and other submarines to strike at the U.S. Navy’s fuel-supply lines. The war situation for Japan is worsening by the day, and as an American invasion of the home islands draws near, this operation may well represent Japan’s last line of defense. Kuramoto Takayuki (Tamaki Hiroshi), Commander of the I-77, has been friends since Naval Academy with Arisawa Yoshihiko (Dochin Yoshikuni), commander of I-81, another submarine on the operation. There are also romantic feelings between Kuramoto and Arisawa’s younger sister, Shizuko. Before he left on this mission, not knowing when he will return, she gave him a hand-written piece of music. The song, entitled ‘Midsummer Orion’ in Italian, is one composed by Shizuko, and she has added a written message to him. ‘O Orion, guide the one I love...’ At this time of year, Orion is only visible at sea for a very short time at dawn. Sailors have long said there is no better omen of good fortune than the sight of Orion at midsummer. Shizuko has entrusted her feelings for Kuramoto to the shining of Orion. Kuramoto and his crew counter-attack against the U.S. destroyer Percival. Its captain, Mike Stewart, has the finest record in the U.S. Navy, and the loss of his younger brother to a Japanese kaiten manned-torpedo attack has only strengthened his resolve to fight. Captain Stewart, with bold but cautious ingenuity, has cut through Japan’s second and third lines of defense, and has already confronted Arisawa’s I-81, deployed in front of Kuramoto. As Japan’s top submarine commander, Arisawa has sunk numerous destroyers, and he fights back as Stewart sees through his strategies, but before Stewart’s originality this line of defense, too, is broken. Japan’s remaining hopes are entrusted to Kuramoto and the crew of the I-77. Now the I-77 and the Percival begin a mutual hunt. A genial smile never leaving his face, Kuramoto is as if advancing chessmen as he coolly reads his opponents moves, turning and striking boldly whenever his enemy shows himself. Against him Stewart utilizes all the optimism and instinct his vast experience has given him, determined to wait until he has achieved certain victory, calm to an extreme degree as he drops his depth charges. The two captains bring all their knowledge and power to bear as, with dwindling supplies of torpedoes and depth charges, they do battle. After three days and nights of fierce fighting, the I-77 weakens and sustains serious damage, and it appears as if it has come to the end of its tether. The kaiten suicide-torpedo crew members aboard beg Kuramoto to let them attack. He faces them, however, and argues. ‘Now, listen. We’re not fighting just so we can die. We’re fighting to live. A man is a man, and a weapon is a weapon.’ Kuramoto, the lives of his young crew members in his charge, is forced by the vicissitudes of battle into a serious decision. With ‘Midsummer Orion’, the music that holds Shizuko’s feelings for him, in his breast pocket, he sets out on a final battle that will mean life or death. Kuramoto Takashi, Commander of the I-77: although he will gamble his life, he has not lost his will to live. Mike Stewart, Captain of the Percival: he will drive his undersea enemy into a corner from which he cannot escape. August, 1945: the fuse is lit on a final battle to the limits of mind and body. Transcending 64 years of time, this story of men in proud battle on the deep-blue sea is now being told.