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.