Lam Mercure, the timid and cowardly countess of the Mercure household, has endured a life of relentless misery. Ridiculed by her own family for her fearful nature, her situation worsened after becoming the second wife of Char, the Earl of Mercure. With her husband, a powerful but perpetually absent mage, the estate's servants torment her without consequence, aware she is too frightened to retaliate. All of this changes when a blow to her head during a bullying incident unlocks the memories of her past life. She recalls that five hundred years ago, she was Aurora, the most powerful witch in history.

Reawakening as her former self, the new Lam refuses to live as a victim any longer. Using her regained magical prowess, she immediately punishes her abusive servants, stands up to her indifferent husband, and sets her sights on a singular goal: securing a divorce and reclaiming her freedom on her own terms. However, her plans for a quiet, independent life are complicated when Char, now intrigued by her dramatic transformation and formidable magic, begins to take a genuine interest in her. To her dismay, she discovers her cold husband is secretly a devoted admirer of the legendary witch Aurora—unaware that she is that very woman.

As Lam navigates her dual existence, she finds her resolve to leave the Mercure estate weakening. She takes charge of the local schoolhouse, discovering a sense of purpose and enjoyment in helping her new family develop their magical abilities, which have stagnated in the modern era where mages typically specialize in only a single element. Her life becomes further entangled with her past when she is reunited with her former disciples, including the antagonistic Épée, who orchestrated her reincarnation and eventually kidnaps her, forcing her husband and allies to stage a rescue.

The story expands from personal revenge to larger political and magical conspiracies. Lam is summoned by the king for a diplomatic mission to the neighboring kingdom of Lèvres, where the first prince takes a suspicious interest in her. As volumes progress, she confronts the powerful Motar Faith, a religious institution that she and her third disciple, Lance, ultimately dissolve. Yet, remnants of the faith persist in the island nation of Hanche, forcing Lam to go incognito by joining a chivalric order to investigate. This mission provides her with a perfect excuse to travel the world, hunting for clues about the whereabouts of her former magic teacher while working to dismantle the faith's lingering schemes for good.