Got around to watching Seto no Hanayome and reading the manga, and I have to say it’s one of the most funniest anime/manga love comedies of all time.
OP: Romantic Summer – SUN & LUNAR
ED: Asu he no Hikari 明日への光 – Hinoi Asuka
A middle-school boy named Nagasumi Michishio and his two parents are on vacation at his grandma’s house, when all of a sudden he nearly drowns in the Seto Inland Sea. Fortunately for him, a mermaid named San Seto saves him. According to the rules of the Mermen, whenever a human discovers a mermaid’s true identity, the said mermaid has to die, the human has to be killed… or the solution that Nagasumi and San choose; Nagasumi assimilating with mermen society and getting married to San. Nagasumi must adapt to the new lifestyle he has to live in, as well as avoiding getting killed by his father-in-law, Gōzaburō, the big boss in of a mermaid yakuza.