From the Instruction Booklet:
Evil is at it again! Zareth, the Devil's Disciple, has cooked up a fiendish plot to bring Zao back to life. Zao is the wickedest wizard in the universe. He is the Emperor of Evil! If he returns, his strength will be beyond imagination. He'll be able to conquer the world and make all things in it his evil slaves.
You, Joe Yamato, are the only one with enough skill and power to stop Zareth. Get yourself to Zao's stronghold, Azuchi Castle, and hurry! The beautiful Alexandra is Zareth's prisoner there, and she is about to face a terrifying ordeal. Zareth plans to steal her soul in order to bring Zao back to life!
Your road is treacherous, full of monsters and evil beings with surprising powers. No one knows what terrors you'll meet, or if you'll be able to survive. You begin the hardest challenge of your life, but you face it with something special... MAGIC!
From the Back of the box:
Blast your enemies with Magic! Hurl Psycho and Sonic to boggle them. Scorch them with Flame! Pound them to dust with Thunder Dragon! The Castle awaits!