Umeshu is a type of Japanese liqueur made with ume plums—a fruit classified as Japanese apricot. Traditional umeshu is produced by macerating white rock sugar and yellow or green ume plums in neutral alcohol. Black sugar umeshu replaces rock sugar with kokuto, a distinctive type of black sugar produced in Okinawa.
Kokuto is made by slowly boiling sugarcane until it transforms into a thick, dark syrup. The base is then dried, and it can be made into larger crumbs or fine powder. This sugar lends umeshu a distinctive darker color and a rich and complex flavor reminiscent of honey and dried fruit.