Humankind faces its twilight in the far future. Having explored every corner of the universe, people have stopped progressing—their lifestyle now dependent on Energy Capsules, a legacy of their past. ​ Yuuki is a boy living in Spica Village, a base for receiving Energy Capsules from the lunar ruins. One night, he meets Miiya, a mysterious girl who crash-landed due to a spaceship malfunction. Their meeting sparks the beginning of an intergalactic journey in search of Yuuki's father, who left for space to unravel the mystery behind humankind's decline.