Seto no Hanayome

Seto no Hanayome begins when Nagasumi Michishio, a middle school student visiting the Seto Inland Sea for the summer, gets pulled into a world where mermaid law and yakuza power rules overlap in the strangest way imaginable. While swimming at Mio Sun Beach, he suffers a crippling leg cramp and starts to drown, until a mermaid named Sun Seto saves him from the water. Her rescue, however, creates a fatal problem: under mermaid law, any mermaid whose identity is exposed to a human must be executed. To protect Sun, the Seto family forces Nagasumi into an impossible bargain: marry Sun, or be killed by Gouzaburou, Sun's father and the boss of the Seto clan. With no real escape, Nagasumi accepts, and the two are pushed into a secret marriage that has to withstand Gouzaburou's relentless attempts on Nagasumi's life, along with the eccentric antics of the many rivals and oddballs who keep crashing into their daily lives. As Nagasumi and Sun navigate this bizarre arrangement, their cover story slowly starts to feel real. What begins as a desperate survival plan gradually becomes a genuine and innocent love, turning a dangerous lie into an unexpectedly heartfelt romance.