Iconographic Disconnect from Western Mermaids. The image of a Ningyo that modern Japanese people envision—a "beautiful female upper body and a fish lower body"—is a product of Western mermaid legends (such as Hans Christian Andersen's *The Little Mermaid*) being imported and taking root from the modern era onward. Prior to this, traditional Japanese Ningyo iconography, as depicted in texts like the *Kaikoku Heidan*, was exceedingly bizarre and grotesque: "a human-like (or monkey-like) face on a scale-covered fish body." The facial features were not necessarily those of a beautiful woman; they were generally depicted as terrifying men, women, young, or old, bearing sharp fangs. The sheer ugliness of this design emphasized the visceral reality of the Ningyo as a "creature from the Other World" and the taboo, grotesque nature of the act of eating its flesh.

Biological Models and the Natural History Perspective. The core of Japanese Ningyo folklore is believed to contain no small amount of misidentification of actual biological creatures. For example, a prevalent theory suggests that sirenians like dugongs and manatees, or pinnipeds like sea lions and seals, served as the models for the Umibozu and Ningyo. Additionally, in inland (river or swamp) Ningyo legends, there are cases where the true identity is speculated to have been the Japanese giant salamander. Edo period herbalists (Honzogakusha) meticulously collected and classified records of these unknown marine creatures washing ashore, attempting to re-examine yokai through the lens of "science" (natural history).

The Curse of "Eternal Life". The "eternal youth and longevity" brought about by Ningyo meat is a universal human desire, yet in Japanese folklore, it is always depicted as two sides of the same coin alongside "tragedy." As the legend of Yao-bikuni demonstrates, one who obtains eternal youth by eating Ningyo meat must repeatedly watch their beloved family members and husbands age and die, forcing them to experience unbearable loneliness and despair (temporal isolation). The Ningyo is a yokai that acts as a cruel mirror, thrusting the "terror of escaping death" directly in humanity's face.