Reportedly observed on multiple occasions by crew members of government-operated "whale research" ships, these so-called "Ningen" (lit. "humans") are said to be completely white in color with an estimated length of 20 to 30 meters. Eyewitnesses describe them as having a human-like shape, often with legs, arms, and even five-fingered hands. Sometimes they are described as having fins or a large mermaid-like tail instead of legs. The only visible facial features are the eyes and mouth.
According to one account, crew members on deck observed what they initially thought was a foreign submarine in the distance. When they approached, however, it became clear from the irregular shape of the thing that it was not man-made -- it was alive. The creature quickly disappeared under water.
Despite their impressive size, there are very few actual reports of Ningen, and none that I can find before 2007. Of course, most of the websites are in Japanese, so if any of our Japanese readers have more insight into the Ningen, I’d love to hear it. This creature may be a modern variation of the mermaid myth, or perhaps people are mistaking the undersides of large rays for a human face.