The player controls Musashi, a boy summoned to the Allucaneet Kingdom by its Princess — named Fillet — to save it from the invading Thirstquencher Empire. Fillet's intention was to summon the legendary Brave Fencer Musashi, who had saved the kingdom from a monster called the Wizard of Darkness 150 years before; she is therefore disappointed when she gets a small boy instead. Nevertheless, Musashi is given the blade Fusion, and charged with the task of obtaining Brave Fencer Musashi's sword — Lumina, the Sword of Luminescence — before the Thirstquencher Army does.

The bulk of the game involves Musashi fighting a variety of enemies, using both Fusion and Lumina, to save the kingdom from various threats (which range from fires breaking out, to an invasion of half-vampire, half-zombie monsters called Vambees), and to acquire five scrolls which increase Lumina's strength and grant Musashi new abilities. There are also several minigames and puzzles scattered throughout which must be completed to advance the plot.