Witch Hunter Robin

Robin Sena is a "craft user", born in Japan and raised by the Roman Catholic Church in Italy. She is trained to use her craft (fire) to hunt down witches. Witchcraft is a genetic trait, dormant within a number of individuals within the human population. However, powers can be "awakened" in these dormant human "seeds" at any time. Trained hunters, usually craft-users or "seeds" themselves, are needed to keep watch over "seeds" and hunt those whose abilities become active, serving in secret organizations, such as the parent branch "Solomon" (and the "STN-J" branch in Japan), as self-appointed police to curtail the use of witchcraft in society.

The series begins when Robin arrives in Japan to gain information for Solomon headquarters about a fabled item that holds the "secrets of the craft" while acting undercover as a new hunter to the STN-J in their efforts to capture witches. It is hinted that she understands something of the STN-J's use of Orbo when she refuses to wear the necklaces the hunters wear with it, claiming it frightens her.

Orbo is a green liquid that negates witch abilities. STN-J's hunters carry small vials of it on necklaces as a form of protection against their targets' craft. Hunters also carry air pistols which fire darts or pellets of orbo that dampen witch powers when it enters the bloodstream. Hunters who are craft-users or seeds can use orbo with little ill effects (their powers are reportedly diminished while using it), but the substance is initially debilitating to normal humans.

As the series goes on, Robin grows increasingly uncomfortable with her role in hunting and capturing other witches. She begins to question the treatment they receive while incarcerated in the mysterious "Factory". Robin begins to worry that she will become a target and grows to suspect that her partner Amon will welcome the opportunity to hunt her. Eventually, Robin does become a target of Solomon and labeled a witch, becoming "hunted". In the end, Robin finds out more about her craft and that of witches than she knew at the beginning.