By using a magic wand (a carpet beater and later a flyswatter) given to her by the legendary Red Comet, she can transform into the titular "Magical Ensign Blaster Mari (魔法の少尉・ブラスターマリ Mahō no Shōi Burasutāmari?)".
Mariko is a fifth grader attending a Zeon elementary school. She eventually receives a magical carpet beater from Char Aznable, transforming into an older version of herself. She pilots the Zaku I Blaster Mari Custom against various Federation RGM-79 GMs and RB-79 Balls. She lives with her father, Michael Starmine, and her two brothers Ban Starmine and Dai Starmine. Her carpet beater was later replaced with a magical flyswatter.