During the episode, the villain Aka Oni attacks, turning a farewell card into an Akanbe (monster). Cure Peace eventually uses her powers to defeat the monster while an energetic rock version of the opening theme plays.
In the Glitter Force adaptation, this is Episode 9: "Lies and Dolls" (or "The Perfect Prank").
Yayoi feels increasingly guilty but struggles to find the right moment to reveal the truth as her friends' kindness makes it harder to speak up.
Her friends—Miyuki, Akane, Nao, and Reika—take the news completely seriously. Overwhelmed by sadness, they immediately begin planning a heartfelt farewell party for her.