Microstomus achne is a species of flatfish in the family Pleuronectidae, native to the coastal waters of the northwest Pacific Ocean, particularly around Japan, Korea, and parts of the East China Sea. The genus name Microstomus derives from Greek mikros (“small”) and stoma (“mouth”), referring to the relatively small mouth characteristic of fishes in this group, while the species epithet achne ("froth") is derived from Greek, refers to its slimy texture. This species is one of several right-eyed flounders inhabiting sandy and muddy seabeds where it is adapted to a benthic lifestyle.

Like other members of the Pleuronectidae family, Microstomus achne undergoes a distinctive developmental process in which one eye migrates to the opposite side of the head, resulting in both eyes being positioned on the upper side of the flattened body. This adaptation allows the fish to lie camouflaged on the seafloor while watching for prey. Its body is oval and laterally compressed, with coloration that blends into the substrate, aiding in predator avoidance and ambush feeding. It primarily feeds on small benthic invertebrates such as worms, crustaceans, and mollusks.

Microstomus achne is valued in regional East Asian cuisines for its delicate, white flesh and mild flavor. It may be prepared grilled, simmered, or lightly fried, and is sometimes used in soups or simple preparations that highlight its soft texture. Compared with larger commercial flatfish, it is more often consumed locally rather than widely exported.

Nutritionally, the flesh of Microstomus achne is high in protein and low in fat, providing essential amino acids along with vitamins such as B12 and minerals including selenium and phosphorus. Like other marine fish, it contains small amounts of omega-3 fatty acids and bioactive peptides that may exhibit antioxidant or antihypertensive effects in experimental studies. The mild taste and tender texture make it suitable for a range of culinary applications where subtle flavor is desired.