Miyu and Shuya are high school students. They have dated for 2 years. Miyu and Shuya have a promise that no matter what, they will watch a movie together on the first day of each new month. When Miyu and Shuya are on their way to the movie theater, Shuya suddenly cancels their date. Shuya seems like he is hiding something and he acts nervous. Later, Miyu goes to the place where she is supposed to meet Shuya, but she witnesses Shuya getting into a car accident. She panics, but when she wakes up she finds herself on the morning of the accident. Miyu keeps waking up on the day when Shuya got into an accident.

In 2199, five years after the Gamilons began an invasion of Earth, the planet has been ravaged by the aliens' bombs. The remnants of humanity have fled underground to escape the irradiated surface. One day, former pilot Susumu Kodai discovers a capsule sent from the planet Iscandar that tells of a device that can remove the radiation from the Earth's surface. The Earth Defense Force rebuilds the battleship Yamato with a new type of propulsion system to make the 148,000 light year trip to Iscandar in hopes of saving the Earth. Within one year, the radiation will drive the rest of humanity to extinction.