On their way to kill the Demon King, the violinist Hamel, pianist Raiel, magess Flute, and female warrior Sizer stop at a little kingdom to defeat a raging monster. The king and queen greet the four as heroes and explain that their daughter has been stolen by a monster that lives in a nearby castle. They all agree to go save the hostage princess and fight the monster. The enemy's stronghold, on the other hand, is highly defended...