One day, the mysterious invader Iros came to the earth and did evil everywhere, disturbing the world. At this critical juncture, 18 girls called "Star Guardians" stepped forward and started fighting with their lives to restore peace for mankind. These 18 girls were hand-picked by the sacred tree "Sacred Tree" and wore the "Star Clothes" granted by the sacred tree, thus gaining special powers. The innocent and cheerful Hoshizuki Miki (voiced by Aya Suzaki), the gentle, mature, steady and considerate Narumi Haruka (voiced by Amamiya Sora), the carefree and lively Amano Nozomi (voiced by Higashiyama Ona), the idol-like Kage Kanon (voiced by Hondo Kaede), and the devilish figure of Serizawa Renka (voiced by Nanjo Aino) are the only beliefs of these girls to take back the polluted land.