The crown prince, Cecil, excels in everything so his life is too easy. One day, when he gets engaged to the daughter of the marquis, Bertia, he's told something peculiar all of a sudden: "Prince Cecil! I am a villainess!!" As she says, according to memories from her previous life, they are in a dating game's world, and she is the villainess who breaks up a relationship between a heroine and Cecil. With her goal to become a great villainess and for her engagement to be broken off, Bertia start to cause one disturbance after another in Cecil's boring days?!