Spunky slum kid Astro gets the chance of a lifetime to end the chaos ripping apart his home planet when the playboy prince switches places with him. Now Astro has become Prince Barrage, a boy charged with the duty of restoring peace to the planet...and given an all-powerful magical spear to do it!

Astro and his loyal knight Tiamat's wild adventure of freeing Industria from alien invaders gets a lot more complicated in the city of Maseille. There they will have to defeat aliens who subjugate the city with a seemingly omnipotent power known as Dark Energy, and whose leader has a deep connection to Astro's past.