The Northern and Southern Seas have been allies for generations, but their royal heirs have never met. That changes when Prince Katsuki Bakugo catches sight of a mysterious mermaid dancing among whale sharks beneath a moonlit ocean. The moment he learns she’s Princess YN of the Northern Sea, he knows he’s in trouble. As diplomacy, duty, and destiny bring their worlds closer together, a connection begins to grow between them—one powerful enough to change not only their futures, but the future of both kingdoms.