Brewed rice vinegar, Kurozu, is a traditional Japanese vinegar with a dark amber color. Kurozu is produced in a regional area of Japan using traditional techniques and made inside handcrafted pottery jars. Kurozu is used as both a seasoning and a healthcare supplement. In vitro and in vivo investigations of ingredients in Kurozu have been carried out. Studies of the functional aspects of Kurozu began in the 1980s, and the health promoting and disease preventing effects of Kurozu have since been elucidated. It was reported that Kurozu improved the symptoms of hypertension, allergies, hypercholesterolemia, enhanced carbohydrate metabolism, and inhibited tumor growth. Kurozu-Moromi is an insoluble product created from the fermentation of Kurozu. Kurozu-Moromi also shows valuable properties, including improvement in dyslipidemia, prevention of hyperglycemia, antitumor effect, and antiallergic activity.