Emi Kobayashi, a young woman who loves otome games, dies and reincarnates into the world of her favorite game, The Star Maiden and the Knight of Salvation, as the villainess Remilia Rose Graupner. Aware of Remilia's tragic fate, the kind-hearted Emi uses her knowledge of the game's events to change the story, hoping to give the character she loves a happy ending. For years, she works to avert the destruction of the kingdom and build positive relationships with the prince and other key characters, and her efforts appear successful.

However, her plans are shattered when the game's heroine, Pina Blanche, reveals herself to also be a reincarnated person. This reincarnator, who views Emi as an obstacle to following the game's original plot, uses lies and illegal love potions to turn everyone against Remilia. Emi is falsely accused of bullying the heroine, has her engagement to the prince broken, and is publicly exiled. The shock of this betrayal, after all her hard work, causes Emi's consciousness to collapse.

At that moment, the original Remilia awakens. Her consciousness had remained inside her body the entire time, watching and experiencing everything Emi did. Moved by Emi's genuine love and devotion, which saved her from becoming a lovestruck villainess, Remilia vows revenge against the fake heroine and the love interests who hurt the gentle Emi. She decides to steal all of Pina's destined accomplishments, clear her own name, and save the world, all with the aid of Anhel, the secret Demon King and a hidden love interest from the game.

The story follows Remilia as she methodically executes her plan. She leaves the kingdom and builds her own domain, using Emi's knowledge to solve every crisis that was meant to make Pina a heroine. Remilia cures a miasma that is destroying the demon realm, forges alliances with the dwarves, and develops new technologies, all while maintaining the persona of a benevolent noble. Her revenge is not direct violence but a calculated campaign to make Pina and the prince irrelevant and humiliated, culminating in a public condemnation where she reveals the truth of their crimes. The narrative explores themes of identity, vengeance, and the profound bond between the two souls inhabiting one body as Remilia ruthlessly pursues retribution for the sake of the woman she calls her "beloved Emi".