In "The Guardian Legend", the player controls the female guardian of Earth, a "robot transformer"; the Japanese version of the game calls her "Miria". The player is to destroy the alien moon Naju before it gets to Earth. The player needs to turn on the moon's self-destruct device and escape the moon before it gets to Earth. Five alien tribes who try to control the moon stand in the way of the player. To help players along, messages left by a person help guide them in finding the safety switches to turn on the self-destruct device. These messages also help players get to some other rooms.