Mumumun! Siren and Hummy's Secret Meow!

Siren decides to leave the Minor Trio, denying accusations that she is Cure Muse, and runs into Hummy. When Siren runs off after Hibiki and Kanade protect her and Hummy from an angry cat, she leaves behind a note sheet. 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. As the Minor Trio lead Hibiki and Kanade away, Mephisto uses his wily ways to put Siren back under his control, convincing her that it was Hummy's fault she lost the contest. She 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.