In the "Great Disaster," Japan has been thrown into chaos by onmyouji (a kind of magician). Harutora Tsuchimikado was born into an onmyouji family, but has no power whatsoever. His estranged sister appears to him one day to take him up the promise he made long ago to become her shikigami (familiar). A battle between onmyouji is about to begin.
