In the year 526 of the Church Calendar, witches exist in the world, and "magic" has become popular. However, the world is still unaware of the existence of "magic". In such an era, there are half-human, half-beast mercenaries who are despised by people as "fallen beastmen". He was coveted by witches every day, and he dreamed of becoming a human, until one day he met a beautiful witch in the forest and changed his fate. "-Want to become a human again? Then mercenary, become my guard!" The witch who calls herself Zero said that her "Zero Book"-a magic book that could destroy the world if used improperly was stolen by someone, and she is now on a journey to find this book. The mercenary accepted the request to become the guard of the witch he hated the most, on the condition that Zero used his power to help him become a human. People's thoughts began to be confused and intertwined around the forbidden magic book... A superb fantasy drama brought by a noble witch and a gentle beastman.