"The Ancient Magus' Bride: Wizard's Blue" is a spin-off of the main series "The Ancient Magus' Bride," focusing on the character Alice, a young mage with a troubled past. The story is set in the same magical world, blending folklore, alchemy, and supernatural elements. Alice, who works as a librarian at the College of Wizardry, is tasked with investigating a mysterious book known as "Wizard's Blue." This ancient tome is rumored to hold immense power and is linked to a series of strange occurrences, including the disappearance of several mages.

As Alice delves deeper into the mystery, she uncovers the book's connection to a powerful and dangerous spell that could disrupt the balance of the magical world. Alongside her familiar, a small dragon named Renfred, Alice navigates the challenges posed by rival mages, hidden agendas, and her own insecurities. Her journey is further complicated by her strained relationship with her mentor, Lindel, and her struggle to reconcile her past with her present.

The narrative explores themes of identity, responsibility, and the consequences of wielding magical power. Alice's growth as a mage and her determination to protect those she cares about drive the story forward. The plot intertwines with the broader lore of "The Ancient Magus' Bride," offering insights into the magical society and its intricate rules. The series maintains a balance between action, mystery, and character development, providing a compelling addition to the franchise.