In 2046 a mysterious alien force launches an attempt to annihilate humanity. Mikako, left alone with the one person she loves, volunteers as an interstellar pilot to fight the invasion. While she endangers herself to protect mankind, Noboru remains on Earth, waiting for any message that might confirm her survival. Days turn into months, then years, as each new communication brings hope or despair. Though Mikako ages little in the timeless expanse of space, Noboru grows older on Earth. The two lovers, separated by vast distances, strive to stay connected as the gulf between them expands at an alarming pace.