In 1918, a young Jiro Horikoshi longs to become a pilot, but his nearsightedness prevents it. He reads about the famous Italian aircraft designer Giovanni Battista Caproni and dreams about him that night. In the dream, Caproni tells him that he has never flown a plane in his life, and that building planes is better than flying them.
Five years later, Jiro is traveling by train to study aeronautical engineering at Tokyo Imperial University and meets a young girl, Naoko Satomi, traveling with her maid. When the Great Kanto Earthquake of 1923 hits, Naoko’s maid’s leg is broken and Jiro carries her to Naoko’s family, leaving without giving his name.
In 1927, Jiro graduates with his friend Kiro Honjo and both are employed at aircraft manufacturer Mitsubishi and are assigned to design a fighter plane, the Falcon, for the Imperial Army. During tests, the Falcon breaks apart in mid-air and the Army rejects it. Dispirited about the seeming backwardness of Japanese technology, Jiro and Honjo are sent to Germany in 1929 to carry out technical research and obtain a production license for a Junkers G.38 aircraft. Jiro sees Hugo Junkers, argues with German guards and witnesses violent antisemitism. He dreams again of Caproni, who tells him that the world is better for the beauty of planes, even if humankind might put them to terrible purposes.
In the spring of 1932, Jiro is promoted to chief designer for a fighter plane competition sponsored by the Imperial Navy, but his design, the Mitsubishi 1MF10, fails testing in 1933 and is rejected. Disappointed, Jiro goes to a summer resort in Karuizawa to rest, where he meets Naoko again. Castorp, a German visitor privately critical of the Nazi regime, thinks the summer resort is a good place to forget bad things, referencing The Magic Mountain by Thomas Mann both in his name and in this thought. He tells Jiro, who intends to visit Dessau, that Dr. Junkers is in trouble for fighting Hitler’s government and calls the Nazis a gang of “hoodlums”. Castorp further tells Jiro that Germany will go to war again and that they must be stopped. Later, Jiro asks Naoko’s father for his blessing to marry her, and the two are engaged. However, Naoko has tuberculosis and wants to wait until she recovers to marry. Castorp assists in the romance before fleeing arrest by the Japanese secret police.
Wanted in connection with Castorp, Jiro hides at his supervisor’s home while he works on a new navy project. Following a lung hemorrhage, Naoko recuperates in a mountain sanatorium but cannot bear being apart from Jiro, and returns to marry him. Jiro’s sister Kayo, now a doctor, warns Jiro that his marriage to Naoko will end tragically as tuberculosis is incurable. Though Naoko’s health deteriorates, she and Jiro enjoy their time together.
Jiro leaves for the test flight of his new prototype aircraft, the Mitsubishi A5M. Knowing that she will die soon, Naoko returns to the sanatorium, leaving letters for Jiro, her family, and friends. At the test site, Jiro is distracted from his success by a gust of wind, suggesting Naoko’s passing.
In the summer of 1945, Japan has lost World War II and has been devastated by air raids. Jiro again dreams of meeting Caproni, telling him he regrets that his aircraft was used for war. A group of Zeros fly past and their pilots salute Jiro. Caproni comforts him, saying that Jiro’s dream of building beautiful aircraft was nonetheless realized. Naoko appears, encouraging her husband to live his life to the fullest.