In this first game of the Cosmic Fantasy series, the player controls a young adventurer named Yuu, who travels through space together with a robotic motorcycle cat called Monmo. One day, their space ship crash-lands on an unknown planet. The heroes realize that the planet is in a civilization phase far inferior to their own space-traveling world, and resembles a medieval society. Upon visiting a village, Yū discovers that the clan of kobolds is threatening its inhabitants. What starts as a simple mission soon turns into a grand quest against an evil force, that will eventually lead Yuu to realize his role as a Cosmic Knight, whose task is to defeat intergalactic evil and save the world.