The Starry Sky World (星空界, Hoshizora-kai) is the home to the twelve Star Princesses who are based on the Zodiac signs and maintain order in the universe. But when the Notraiders attack the Star Palace, the princesses scatter themselves across the universe as the Princess Star Color Pens. Seeking to revive the princesses and avert the universe from being consumed in darkness, the aliens Lala and Prunce travel with the fairy Fuwa to Mihoshi Town (観星町, Mihoshi-chō) on Earth where they meet the imaginative Hikaru Hoshina. Receiving a Star Color Pendant and one of the Star Color Pens, Hikaru transforms into the legendary PreCure, Cure Star. Joined by Lala and two other girls, Elena and Madoka, as well as the shapeshifting cat-like alien, Yuni, Hikaru leads the Star Twinkle PreCure as they seek to revive the Star Princesses and fight against the Notraiders.