In the world of Witch Hunter Robin, witchcraft is a genetically determined gift, but not everyone uses it for the right purposes. An organization called SOLOMON works against people who misuse witchcraft, called witches. One of SOLOMON's members is Robin Sena, a Japanese woman raised by the Catholic Church in Italy and trained there to use her gifts against witches. When Robin travels back to Japan for SOLOMON to hunt witches, over time she becomes uncomfortable in her role and begins to doubt her organization and how they deal with witches.