In the distant future, trains are no longer bound by their physical tracks. Instead, they take to the skies and travel across the universe on the Galaxy Railways, transporting mankind from planet to planet. However, the Galaxy Railways are no safer than traditional trains: criminals, terrorists, and vile aliens always find a way to stir up trouble.

Manabu Yuuki, a rash and hot-headed man, is the latest addition to the Galaxy Railways' elite Space Defence Force (SDF). These brave men and women are responsible for protecting the railways and responding to any unprecedented danger, risking their lives to protect the innocent from evil. But as this drama unfolds and the SDF's greatest crisis draws nearer, Manabu must truly learn what it means to be a member of the SDF before it is too late.