Selah, an ordinary marine student, suddenly finds herself reincarnated as a minor character in a novel. Determined to fulfill her own dreams even within the story, she begins meddling in the original plot. The one thing she absolutely wants to avoid? Getting involved with the dark and enigmatic Admiral Elaim. But then she uncovers a shocking truth: Elaim, who rules the lawless seas, is actually a legendary mermaid, a siren. Unexpectedly gentle yet constantly drawing her in, Elaim forces the sea-bound slacker in training Selah into repeated encounters. Overflowing with magical power, he needs Selah’s help to survive. Amid the waves of fate, the two of them navigate a refreshing, heartwarming romance on the open sea.