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.

Piece by piece, Alto, Elva, and their allies are unraveling the secrets of the kannagi, the mysterious black sea, and their isolated island home — but every new revelation only brings more questions. After confronting Lord Shiyan and his own painful childhood, Elva finally feels that he is ready to deepen his connection with Alto, and for the two of them to become lovers in truth. But Alto is coming face to face with painful truths of his own as the origins of his healing abilities and immunity to the black sea finally come to light.