The Samebito (shark man in Japanese) is a creature that appears in "The Gratitude of the Samebito", a short story by Lafcadio Hearn.
It is described as a humanoid with inky black skin, emerald green eyes, a face like a demon's, and a beard like a dragon's.
Hearn's story appears to have been based on another story called Kojin by Kyokutei Bakin. The kojin are creatures thought to live in the South China Sea, which resemble ningyo, are always weaving at their looms, and whose tears become jewels.
In the story, a man named Totaro met the Samebito one day on a bridge. Although it seemed frightening, the creature turned out to be a gentle being who, as punishment for a petty fault, has been expelled from the sea by his former employer, one of the eight great Dragon Kings of the ocean. Totaro took pity on the creature and allowed it to live in a deep pond in his garden, giving it food and shelter. Some time later, Totaro fell in love with the beautiful Tamana, who she saw at a female pilgrimage at Mii-dera and intended to marry her. Tamana's father, however, had set the bride price at 10,000 precious stones. Unable to come up with such an immense fortune, Totaro went home and lay ill until he was dying. When the Samebito learns that his master is on his deathbed, he begins to cry tears of blood which become precious rubies when they hit the ground. Through the Samebito's tears, Totaro eventually wins the hand of the woman with whom he is infatuated. When he has finished weeping, the Samebito is also pardoned by the dragons and returns to the sea, and the story ends happily.