Keiti Kiiro becomes entrusted with the color yellow. After that, she walks on the street, to see a giant shadow attacking Sutoroberi City. She transforms, to be shocked by it. The shadow shoots a beam at Keiti, and she launches her attack. The shadow dies, but Keiti ends up getting sick, for if the shadows Rainbow Princesses battle don't miss on their beam, the Rainbow Princess gets sick after the battle. The next day, Keiti feels better, and is informed by a man named Ryo that there are other Rainbow Princesses like her. Keiti vows to search for them, but little does she know her best friends are two!