The Leatherjacket fish also known ，belongs to the family Monacanthidae under the order Tetraodontiformes. It is a small to medium-sized warm-temperate marine fish widely distributed along the coasts of the Yellow Sea, East China Sea, and South China Sea, as well as Japan and the Korean Peninsula in the northwest Pacific.

The ma-men fish has a diamond-shaped, laterally compressed body with a protruding snout resembling a horse's head, hence its name. Its skin is smooth and scale-less, with a gray-brown or bluish-gray dorsal surface and a lighter belly. The fish has long dorsal and anal fins, and is known for its agile swimming ability. It mainly inhabits nearshore, upper to middle water layers, feeding on plankton and benthic invertebrates.

The flesh of the ma-men fish is delicate, firm, and moderately fatty, with a mild and delicious flavor. It is rich in high-quality protein, unsaturated fatty acids, and various vitamins. It is commonly prepared by steaming, braising, frying, or grilling. In Japan, it is called "Kawahagi" and is often used in sashimi. The fish's liver, known for its rich flavor, is commonly served with a special liver sauce, making it a winter delicacy highly sought after in Japanese cuisine.