When pirate captain Dazai tries to throw himself overboard, he's saved by an unlikely hero-a silent, kind-eyed mermaid named Chuuya. Their worlds collide when Chuuya, fascinated by Dazai's hat, tries to trade a gem for it. Instead, Dazai impulsively brings Chuuya aboard his ship-"mernapping" him in the process. Through laughter, confusion, and small acts of kindness, the two begin to understand each other, even without words.