The most popular of the many species of flatfish found in Japanese waters, the olive flounder, or hirame, is a challenge to catch and a gourmet treat.

With both eyes on the same side of their body, flatfish are among the more distinctive-looking creatures in the sea. When very young they have an eye on each side of their body like other fish, but as they mature, one of the eyes migrates. The giant halibut of the North Pacific and the marbled sole commonly found in Tokyo Bay are right-eyed flatfish, with both eyes on the right sides of their bodies. Olive flounders, along with close cousins summer flounder and California halibut, are left-eyed.

In Japan, olive flounder (Paralichthys livaceus) can be found in waters from Hokkaido to Kyushu, where they lie in the bottom sediment with only their eyes exposed. The flounder's blind side is white, but the other side is a camouflage blend of olive or brown with dark blotches and white spots, making it almost invisible to the small fish and crustaceans it feeds on.