The main characters are four human teenagers and their fairy partners (called "muglox" according to ShoPro/Viz Media materials). Each set of four has complicated relationships which are the driving force of the story. In addition, there is a large cast of supporting characters, including regular characters, some of whom change with each arc (original, Wonderful, Golden, and Enchanted seasons, as well from the Murumoya fansite; for details, see "List of Mirmo! media"). The fairies use musical instruments as their magical tools.