Major Land is a vibrant musical realm where instruments and notes come alive. During an annual concert, Hummy, the cat songstress of Major Land, prepares to perform the "Melody of Happiness," a song capable of spreading joy to worlds beyond. However, Mephisto, the king of Minor Land, interrupts the event and rewrites the score into the "Melody of Sorrow"—a dissonant composition that would cause despair if performed. To prevent this, Hummy is tasked with finding the Precure, renowned warriors with an unmatched passion for music, and recreating the Melody of Happiness. Hummy arrives in Kanon Town, home to musically inclined athlete Hibiki Houjou and studious baker Kanade Minamino. Hibiki and Kanade, formerly best friends, have since fallen out of touch and engage only in endless bickering. Their activities are abruptly halted by an unwelcome guest—the songstress of Minor Land, Siren. When Siren transforms an important record into a gigantic monster, the girls' hearts resonate with the desire to protect what they hold dear, and the two transform into the Suite Precure! As legendary warriors, Hibiki and Kanade must put their personal squabbles aside if they wish to protect the happiness of the world.