Couple hundred years have passed, and people are hardly heard about witches nowadays. However, a leading secret organization in witch management is still exists. This Salomon's witch management organization, STN (not sure what STN stands for), has a task to capture the remaining witches. As a leading secret organization in witch management, STN's influence has reached the government and police organizations across the world. As the recent change in Japanese society has led into increasing of witch activities, STNJ (STN Japan branch) assembled a group of hunters to draw a desperate last-minute fight against witches. However, the mysterious death of one member from the group has led to morale decrease into STNJ. In order to help STNJ, a lone 15 years old replacement girl is sent by Salomon directly to Tokyo. Sena Robin, a craft user, can she be really the key to win this fight?