Set in a distant future, where the world is a vast expanse of water and scattered islands echo the golden age of piracy. Kasai, a 17-year-old, is forced from his village after a devastating storm. Alongside a group of pyrates with an unknown connection to his mother, his quest to find his missing father thrusts him into the sights of a formidable pyrate, but their interest in him is a mystery.

During a confrontation, Kasai unexpectedly unlocks latent powers, but mastering them becomes a race against time as his foe pursues him. After a confrontation leaves his abilities wanting, he soon learns that his foe has targeted his brother's family and Kasai must race to save them. But can Kasai beat a foe that has yet to yield to him? And will his father, who Kasai knows is nearby, finally reveal himself?