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 I think : 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?