Pure‑blood deep‑sea princess Calista has a three‑hundred‑year‑old engagement to her playboy fiancé Tristan. The heir to the sea royal family Xavier has loved her in secret for five hundred years. He plots carefully to drive the couple apart. He exposes Tristan’s infidelity, saves Calista right after her fiancé drugs her, and enters a sacred bond with her. Once Tristan reveals Xavier’s schemes, Calista sees through his selfish nature. She chooses Xavier, who has always guarded her sincerely. She finally gets over the gratitude from a life‑saving incident five hundred years ago and holds a royal deep‑sea wedding.
