Night after night, Elva steps forth into the black sea with sword in hand, driving back creatures that surge forth from the waves - for he is one of the ‘kannagi,’ white-haired, ageless warrior priests chosen by the divine to protect the people of the island. Although kannagi are destined to live short and lonely lives, Elva has found devoted companion in Alto, whose touch heals the black stains left by the cursed sea, and who has sworn to serve him and free him from his cursed fate. But painful revelations threaten their bond as the secret behind Alto’s miraculous power is revealed - a truth so devastating that Alto finds he cannot share it even with his beloved Elva. As tensions mount and fear and distrust toward the kannagi reach a fever pitch, the return of Mikhail - a kannagi thought long-dead and Elva’s former best friend - only throws things into further chaos. Why has Mikhail turned his sword against the people of the island? What painful secrets are hidden in the depths of the black sea…and will Elva lose himself in the unrelenting tide of old wrongs that cry out for vengeance?