Archetypes: Mermaids in Manga

Vampires are a common trope across cultures. So are mermaids although their historical form in Japan is fundamentally different from that found in The Odyssey and other Western myths.

"Mermaids" in Japan fall under the yokai classification. Yokai can be translated as "bewitching spectres". Although some yokai have human shape, the animal part of the creature almost always overwhelms the human. Two that stand out:

Kappa: humanoid demons or imps that lurk near water.

Pearl diver in Japan

Ningyo: part human/part animal--not the sirens of Western literature yet still supernatural since eating the flesh provides long life.

The lack of mermaids with beautiful upper human halves in Japanese lore may be explained by two factors--the existence of real, female pearl divers in Japan (why go supernatural when you have the real thing?) and the fact that so many Japanese gods/dragons (who occasionally take human form) live near or on water to begin with. (Water is rather difficult to ignore in Japan.)

Whether an internal product or a product of Western influence, more-human-than-beast mermen and mermaids are a current staple of manga and anime. They utilize many of the same characteristics as Western merpeople, being selfish, self-centered, amoral, and demanding. In yaoi, they inevitably show up in some hardworking salaryman's tub, demanding food and special treatment. Selfish Mr. Mermaid by Nabako Kame states the fact of the merman's personality upfront! The merman is unquestionably the seme.

The connection between amorality and merpeople is fairly old and seems to be connected, at some level, to the trope of the sea as a changeable, indifferent force that cannot be controlled or understood and doesn't play favorites.