Tenaga-jin is one half of a pair of youkai said to be found on the island of Kyūshū, the Ashinaga-tenaga ("long legs long arms"). Tenaga has extremely long arms and collaborates with Ashinaga-jin to catch fish by climbing on his back and using his long arms to reach the fishes in the sea.
The Tenaga-jin are most likely based on the Zhangbimin (長臂民), literally the Long Armed People, a tribe first recorded in the Shanhaijing, an ancient compilation of the mythological geography and beastiary of pre-Qin China. It was said they lived beyond the eastern sea. The records state that when a group of explorer ventured to the eastern borders, they asked an old man there if there were any countries beyond the eastern sea. He replied that a cloth garment with sleeves thirty feet in length had been found in the sea. The explorers fitted out an expedition, and the discovery of the Long-armed Country was the result. Their country bordered the Changtuimin (長腿民) and the two peoples mutually assisted each other, those with the long arms being able to take the shellfish of the shallow waters, while those with the long legs take the surface fish from the deeper localities; thus the two gather a harvest otherwise unobtainable.