Crown Prince Cecil married Bertia, a self-proclaimed "villainess". While enjoying their newlywed life, Bertia's friend, Princess Risona, asked her to be the producer for her wedding. While supporting Bertia, who was full of enthusiasm, the two went to the kingdom of Cielby, but Bertia was acting strangely. Bertia suddenly declared, "I will be the substitute villainess for Princess Risona!"

Bertia and Cecil are in Cielby to produce and attend the wedding of Umube's Princes Risona and Cielby's Crown Prince Alayce. Bertia, who declared that she will act as the “ substitute villainess” for Risona, put various plans into action, but ......? In addition, in order to be useful to Risona, Bertia almost goes out of control and says, "I'm going to do my best to take down Prince Ramtak!"

In the Kingdom of Cielby, Bertia has declared herself the “Substitute Villainess.” Her plan? To play the part of the bully. The problem? Her supposed target, June, has become hopelessly fond of her instead! While Bertia struggles with her failing villainy, she attends a tea party where she hears a startling a Holy Maiden once saved the kingdom by offering her blood to the Snake Deity. “I’ve just remembered something important,” Bertia tells Cecil. Just then, a two-headed snake appeared before her...!