Siren decides to leave the Minor Trio, then Hummy then explains the history of when she and Siren were best friends. When some other fairies tried to play a trick on Hummy during a singing contest, Siren helped Hummy out, allowing her to earn the chance to sing the Melody of Happiness. Siren becomes moved by Hummy's words of friendship. Siren creates a Negatone from the music sheet which corners Hibiki and Kanade, but Cure Muse appears again, encouraging them to defeat it. After the battle, Hibiki, Kanade and Hummy must find a way to convince Siren back to her good self.