On Khen Island lies a mysterious legend: alongside humans live another species—mermen. On land they appear no different, but once in the sea, their true form is revealed. Phurich, arriving from Bangkok to co-manage a bar with his friend Phana, quickly develops feelings for bartender Nava. But one night, after drinking, Phurich stumbles to the shore and falls into the water and catches a glimpse of what seems to be a merman.

After waking from a hangover, Phurich wonders if he truly saw a merman the night before. He mentions it to Phana, who brushes it off, yet later questions Nava privately to uncover the truth. Meanwhile, Phurich pursues Nava, sparking a rivalry with Phraphai. But rumors spread across the island of several missing mermen—will this looming danger disrupt the course of their feelings?

Phurich unexpectedly barges into Nava's home and continues to pursue him boldly, though Nava thinks he's just a flirt. As they discuss the island's mermaid legends, Nava confesses that mermaids and humans cannot coexist, but Phurich believes that true love can overcome all boundaries. With Phurich's direct approach and Nava's secret identity, how will this forbidden relationship unfold?