Master ninja Hiro Hattori and Jesuit Father Mateo head up to Mount Koya, only to find themselves embroiled in yet another mystery, this time in a Shingon Buddhist temple atop one of Japan's most sacred peaks. November, 1565: Master ninja Hiro Hattori and Portuguese Jesuit Father Mateo travel to a Buddhist temple at the summit of Mount Koya, carrying a secret message for an Iga spy posing as a priest on the sacred mountain. When a snowstorm strikes the peak, a killer begins murdering the temple's priests and posing them as Buddhist judges of the afterlife—the Kings of Hell. Hiro and Father Mateo must unravel the mystery before the remaining priests—including Father Mateo—become unwilling members of the killer's grisly council of the dead.