The best known manga mermaid series is Mermaid Saga by Rumiko Takahashi. Rumiko Takahashi is one of the most famous and successful manga writers in Japan. Her other series, Urusei Yatsura (Those Obnoxious Aliens) and Ranma 1/2, are classics, especially the former. Her mermaid stories differ from her other work in that they are horror stories!
In Japan there is a legend that if you eat the flesh of a mermaid you will become immortal. Well, yes, but there is one problem. Everyone who eats the flesh of a mermaid becomes immortal, some remaining as they are for all eternity, but many others are transformed by it into monsters. They may take on the actual forms of monsters, or they may keep their human form but become dangerously psychotic.
The manga Mermaid Saga follows the adventures of Yuta and Mana. Yuta was a fisherman who became immortal 500 years ago,Mana a young girl who became immortal recently. Together they are searching for a living mermaid to tell them how to ride themselves of the curse of immortality! The curse of living forever while all around them age and die.
In the course of their search, they encounter others who are looking for immortality or who have found it. The ones who have found it are the unlucky ones.
If you are not familiar with Japanese manga you need to know that generally speaking it is much more violent and sexy than American comic books usually are. Mermaid Saga is certainly no exception. It is full of unpleasant images and disturbing acts of violence. It is a good story but you have been warned. The manga Mermaid Saga is composed of 4 volumes, plus there are two others called Mermaid's Scar and Mermaid's Gaze. Click here to go to my anime page for this manga mermaid.
Moon Child is a manga based loosely on Hans Christian Andersen's Little Mermaid. It assumes that the events in that story really occurred (with some major changes) and the characters today are living with the aftermath.
The story is set in present-day New York City were Shona, a merman, meets a boy with amnesia he calls Jimmy. Mer-people live in outer space and only return to Earth once every couple of hundred years to mate. Shona has come to New York to find his mate.
The secret is that "Jimmy" is really Benjamin, a beautiful mermaid and Shona's dream girl. Jimmy is in the premature form were he appears to be a young boy. In the spring he will mature into the lovely Benjamin.
Moon Child has the same sort of gender-bending relationships that you find in Ranma 1/2. The difference is that Ranma plays them for laughs while Moon Child is serious. They give the story a strange homosexual overtone. This is one manga mermaid that is definitely not for the kids. At least not American kids.