Ep. 1: Teenager Nagasumi Michishio marries mermaid Sun Seto after being rescued from drowning

While drowning in the ocean near Seto Island, teenage boy Nagasumi Michishio is rescued by the chivalrous mermaid Sun Seto. Strict regulations within mermaid society dictate that both individuals must enter into a marriage to ensure their continued survival. Unaware of the true nature of Sun's clan, Nagasumi finds himself bound to a group that operates as a yakuza organization. This unexpected union forces the young man to navigate the dangerous and complex world of the underworld, hidden beneath the guise of a traditional mermaid family structure, as he adjusts to his new life and the severe consequences of breaking their ancient laws.

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