Right after moving to a small seaside town, Kiko comes across a boy who is abused by the mother. She finds herself in him for being a "52-hertz whale", a lone whale that can only speak in a high frequency other whales cannot hear in the vast ocean. Having been saved by an important friend Ango in the past herself, Kiko decides to save this lonesome boy. It turns, however, into an emotional journey to look back her own past…