After hitting her head particularly hard one day, Duke Claes' daughter, Katarina, suddenly recalls all the memories of her past life: that of a teenage Japanese girl. Just before her untimely death, this girl recalls playing an otome game... that is exactly like the world she's living in now!

She is now Katarina Claes, the antagonist of the otome game, who nastily hounded the protagonist until the end. Knowing all the possible outcomes of the game, she realizes that every single possible route ends with Katarina being murdered or exiled! In order to avoid these Catastrophic Bad Ends, she has to use her knowledge of the game and her own wiles, starting with breaking off this engagement with the prince...