The Plot To Godzilla Minus One
In 1945, at the end of World War II, Kōichi Shikishima, a kamikaze pilot, feigns technical issues with his plane and lands on Odo Island. A dinosaur-like creature, Godzilla, appears during the night and attacks the island, killing everybody except Kōichi and the lead mechanic, Sōsaku Tachibana, who blames Kōichi for the deaths of the others.
In 1947, two years after the war, following his return to Tokyo, Kōichi is plagued by survivor's guilt. He has started a relationship with Noriko Ōishi, and they have adopted a child, Akiko, whose parents were lost in the bombing of Tokyo. Godzilla is mutated and enlarged by the U.S. nuclear tests during Operation Crossroads, and it destroys several U.S. warships before heading for Japan. Citing tensions with the Soviet Union, the U.S. refuses to aid Japan.
Working aboard a minesweeper called the Shinsei Maru, Kōichi meets scientist Kenji Noda. The minesweepers' crew is tasked with stopping Godzilla's approach to Japan. They release a mine into Godzilla's mouth and detonate it, but Godzilla regenerates from its injury.
The heavy cruiser Takao then arrives and engages Godzilla but is subsequently destroyed when it unleashes its heat ray.
Kōichi tells Noriko about Godzilla's attack, expressing his survivor's guilt to her. Godzilla makes landfall in Japan, attacking Ginza in Tokyo. Noriko witnesses the attack while Kōichi attempts to rescue her. Meanwhile, the Japanese military attempts to engage Godzilla, but it fires its heat ray, decimating Tokyo and seemingly killing Noriko among thousands of others.
While Godzilla returns to the ocean, Kenji proposes a plan to kill Godzilla. However, the government refuses to help, leaving it up to the remaining civilians and Naval veterans to enact it. Kōichi recruits a reluctant Sōsaku to repair a broken-down prototype Kyushu J7W Shinden fighter, which Kōichi will fly into Godzilla's mouth and destroy it from the inside. Meanwhile, Kenji plots to destroy Godzilla by surrounding him with Freon tanks and rupturing them, lowering the water's buoyancy and sinking it to a depth of 1,500 meters, letting the resultant pressure crush it. Should that plan fail, balloons would be inflated under Godzilla to force it back to the surface, killing it through explosive decompression.
Godzilla is taken down to 1,500 meters but manages to survive. The balloons are activated, forcing Godzilla up to 800 meters, but it manages to break free. Two ships try to haul Godzilla to the surface but don't have enough power to do so. A fleet of tugboats lend their assistance, and Godzilla is brought to the surface, injuring but not killing it. Enraged, Godzilla prepares to destroy all the ships with its heat ray.
However Kōichi flies the plane into Godzilla's mouth, destroying its head and overloading its heat ray, which destroys the rest of its body. The crew assumes Kōichi sacrificed himself to stop Godzilla's heat ray, but they look above to find that he ejected from the plane. They cheer and salute him. It is revealed that Sōsaku forgave him and told him about the ejector seat, telling him to live.
Back at the port, Kōichi receives a telegram and heads to the hospital with Akiko, where he reunites with Noriko, who survived the destruction, albeit with what appears to be radiation sickness.
Meanwhile, a chunk of Godzilla's remaining flesh sinks to the bottom of the ocean and begins to regenerate.