The Nonoyama sisters, Fū and Rui, were once inseparable, but have recently grown apart. Fū is a cheerful and naive elementary school girl, while her older sister Rui is a more composed middle school student whose past hospitalization made her reserved, despite a former love for singing. Their strained relationship is upended when Fū encounters a mysterious spaceship and gains magical powers. At that exact same time, without either knowing, Rui also obtains magical abilities. This magic transforms each girl into the idealized adult version of themselves: Fū becomes the idol Lily Konpeto, and Rui becomes the idol Lulu Mashū.

However, this power comes with two severe conditions. The magic can only be used for one year, and under no circumstances can anyone discover their secret. Two feline creatures from the magical realm of Felix Star, the grumbling free spirit Uguisu and the calm and charming Azuki, are sent to assist them. As the sisters pursue their separate double lives as magical idols, they remain completely unaware that they share the same fate. The story deepens when an idol named Tōko Kandachi, who founded her own agency called Production Once More, discovers Lily and scouts her for a professional debut. Tōko also brings in a classmate named Sena Aozono to form an idol unit. The series follows Fū and Rui navigating their individual journeys of transformation and performance, all while keeping their magic hidden from the world and, most painfully, from each other, as the one-year limit of their powers steadily counts down.