Early Taisho era.

Yuu, born as the child of a mistress to the prestigious Toudou family, was oppressed and treated like a slave from an early age.

In particular, Yuu's half-sister Nadeshiko pretended to be friendly with Yuu in front of Shinnosuke, who she had a crush on, but secretly bullied her.

Yuu wanted to be free one day, but her wish was not granted as she could not abandon her mother, who was imprisoned in a confinement room.

One day, her mother died in a fire of unknown cause, and Yuu went to help her, but was never heard from again.

--Seven years later, Yuu, who was thought to have disappeared, has grown up to be a beautiful new person, changes her name to "Haruhi," and returns to the Toudou family, where she begins her revenge with the memory of her murdered mother in her heart.