The story begins with Melodia Nonoir recounting a cherished childhood memory of finding and caring for a stray white puppy named Furumoff. Despite her deep affection and the puppy's apparent intelligence and companionship, Furumoff mysteriously disappeared after only a month, leaving Melodia with a lasting sense of loss.
Eleven years later, Melodia, now eighteen and an orphan, works as a magic soldier in the Royal Knights' Seventeenth Patrol Unit. She is a skilled healer but struggles financially, saving diligently for her future. On her eighteenth birthday, she receives a letter from her deceased parents, intended to be opened upon reaching adulthood.
Her mundane life takes a dramatic turn when, after a mission, she experiences a sudden, debilitating seizure. Upon regaining consciousness, she discovers she has transformed into a dog. Initially panicked and unable to speak, she is found by her captain, Millie Toll, who, despite the unusual circumstances, takes her in and cares for her. During this time, Melodia experiences the simple joys of being a dog, including playing fetch and enjoying luxurious baths.
The next morning, Melodia returns to her human form but is still unable to fully control her transformation. Millie, a kind and supportive figure, helps her navigate this new reality. Melodia learns from her parents' letter that they were "Loups-Garous," a werewolf-like race capable of transforming under the moon, and that she might inherit this trait. The letter also mentions a powerful family, the Fenrirs, who are interested in beastmen and with whom her parents had made arrangements.
Following her parents' letter, Melodia is transferred to the prestigious Fenrir Knights, a private force dedicated to fighting "Wolf Witches." Upon arrival, she is shocked to discover that the head of the Fenrir family and captain of the First Cavalry Unit is Dietrich de Fenrir, a man who appears as a large, white dog and who, mistaking her for someone else, proposes marriage. Melodia, still grappling with her own beastman nature and the revelation that her parents were killed by a Wolf Witch, is overwhelmed.
Dietrich reveals that his family has been at war with Wolf Witches for centuries, and that these witches transform humans into wolves. He believes Melodia's parents may have been involved in a past incident related to this conflict. Despite her initial confusion and the overwhelming circumstances, Melodia agrees to join the Fenrir Knights and fight alongside Dietrich and his brother, Gilbert, who also seems to have a keen interest in her. She is given luxurious accommodations and a personal maid, Ruri, further highlighting the extraordinary circumstances of her new life. The narrative concludes with Melodia accepting her new role and the daunting task of confronting the Wolf Witches, while also dealing with the peculiar romantic advances of Dietrich.
