The boy who serves as a shadow substitute for the duke's daughter is adored by the beautiful crown prince.

Euclid Valfischtein, the first prince and crown prince of the Kingdom of Valfischtein, is engaged to Quinn Feelia, a duke's daughter. Euclid treasures Quinn very much. However, Quinn harbored a secret. It was that she was a commoner serving as a shadow double for the Duke's daughter Quinn Feelia, and moreover, an even greater secret—that "she" was not actually a "she" at all, but a "he," in other words, a man.