I'm the Villainess, so I'm Taming the Final Boss

During her public denouncement, Aileen Lauren Dautriche suddenly remembers her past life. She's the villainess from an otome game she once played that will die in terrible ways! She must survive! The best way to ensure her survival? Tame the last boss!

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 finds out that Cedric's new fiancée, Lilia Rainworth, has received threatening letters that were signed by herself. Since she has no memory of doing so, she has her friends help her find out the truth. On the night of the ball, Aileen attends wearing the dress and accessories given to her by Claude. At the same time, Lilia appears at the demon lord's castle.

Aileen finds out that Claude's aide, Keith Eigrid, has been selling demons. Keith tells Aileen about the reason why and reminisces about their past. Now that Aileen knows his true feelings, she decides to cooperate with Keith to prevent Claude from despairing about humanity and turning into a demon. At the same time, Cédric and Lilia visits the demon lord's castle to tell Claude Keith's secret?!

Aileen, now engaged to Claude, hears of a demon attack in Mirchetta. Sensing danger, she infiltrates Mische Academy to investigate. There, she meets James Charles, the last boss of Regalia of Saints, Demons, and Maidens 2, and the quirky student council members.

James turns into a demon earlier than in the game, but Aileen believes he can revert and lets him escape. Student council member Walt doubts Aileen's true identity. Aileen exposes Walt and Kyle's identities, leading to a temporary alliance to solve the vampire case. Mische Academy receives another statement from Ashtarte.

James is wary of Aileen knowing his demon form, but Ribbon and her words soften him. They collaborate on the case. At the school festival, Aileen and James patrol in duck costumes. Claude visits the festival, meeting Aileen again while entering the swordsmanship tournament.

Irene enters the White Lily Contest, knowing that the prize is poisonous demonic incense. She charms everyone in her dress, and James asks her to dance. They were victorious, but the mastermind released a demonic incense and James was transformed into a demon despite their efforts.

Aileen infiltrates a black market auction trading demon incense and meets the sorcerer Elephas Levi. Levi, the final boss of the Regalia of Saints, Demons, and Maidens fan disk, wishes Claude to reconsider the Levi family's treatment. Later, Aileen learns Claude has been stabbed in the abdomen by someone.

Claude loses his memory and magical powers, becoming human. To showcase this aspect, he inspects the third zone of the capital while Aileen follows, trying to confirm her position as his fiancée but experiences unrequited love. Returning to the demon lord's castle, she finds Selena Gilbert fighting Auguste Zelm for demon incense.

A misunderstanding separates Aileen and Claude. Aileen believes dissolving her engagement with Claude and focusing on work will save her. Claude sends her a dress for the ball, but remains cold when she tries to seduce him. Giving up, she dresses as a duck for the ball and is shocked by Claude’s unexpected words.

Aileen is imprisoned in the sorcerer's village, learning of the Levi family's coup initiated by Lilia, who serves the empress dowager. Winning over Elephas, branded as a traitor, Aileen escapes. They rush to save the Levi family and Claude, only to confront Lilia wielding another holy sword.