After breaking off the engagement, Prince Cedric seizes all of Aileen's businesses. Aileen is in danger of being disowned and becoming a commoner if she doesn't recover the financial losses of the Dautriche family before the ball in two months...

Aileen overcame all the difficulties and got engaged with Claude. Just when she thought she found her happily ever after, she receives news that a demon named Ashtarte attacked a human village in the Mirchetta region. Sensing new dangers, Aileen infiltrates Mische Academy in the Grand Duchy of Mirchetta to investigate the situation. There, she meets James Charles, the last boss of Regalia of Saints, Demons, and Maidens 2 as well as the other quirky members of the student council.

"James is suspicious of Aileen since she knows of his demon form. However, Ribbon's existence and Aileen's words ""I want to protect you"" softens his heart and he decides to work with her on the case. The day of the school festival finally arrives and Aileen patrols the area with James in duck costumes. Meanwhile, Claude tosses his work to the side and goes to the school festival to have some fun. He meets a certain duck again when he entering the swordsmanship tournament."

Aileen and Claude get separated by a misunderstanding. Aileen stubbornly decides she can avoid getting executed if she just dissolves her engagement with Claude and buries herself in work. Soon, she receives a dress from Claude for the upcoming ball. He's cold when she tries to seduce him, but he chases after her once she gives up...... The confused Aileen shows up to the ball dressed as a duck, but is blown away by the words that comes out of his mouth.