Yoake no Uta

Each night, Elva enters the dark sea with a sword to battle creatures emerging from the water. He is a "kannagi," a warrior priest chosen to defend the island. His white hair and unchanging youth contrast with the blackened parts of his body, signs of a corruption that slowly kills all kannagi. The islanders fear and avoid him until he meets a boy named Alto. Impressed by Elva’s power and solitude, Alto vows to serve and help him escape his fate. Over eight years, Alto becomes a strong and brave young man, remaining loyal to Elva. Though Elva expected to die soon, his condition appears to improve in Alto’s presence.