Lucian, a mafia don, bears the curse of the Oath of the Sea, which torments him with agonizing pain every full‑moon night. Caelum, the merman prince, infiltrates Lucian’s circle under a false identity to reclaim the sacred relic — the Heart of the Deep. To break Lucian’s curse, the two enter into a contractual political marriage.
What begins as mutual exploitation gradually blossoms into a bond forged by life‑and‑death ordeals. They endure bitter separation and Lucian’s remorseful pursuit to win Caelum back, alongside tangled feuds between powerful clans. Having weathered all hardships, they choose each other whole‑heartedly, and finally unite in a legendary wedding ceremony.
