30 Masters of Wine from Around the World Head to Yamanashi to Test Koshu on the Ground

The Master of Wine (MW) is a qualification awarded by the Institute of Masters of Wine, based in London, and is regarded as the most prestigious in the wine trade. Only around 420 people in the world hold it. In March 2026, 30 of these MWs gathered in Japan for a five-day tour of wine regions. The participants came from Europe, the United States, Singapore, Australia, South Africa and India. After a seminar and tasting in Tokyo and a visit to Nagano Prefecture, the group travelled to Yamanashi Prefecture, west of Tokyo. Yamanashi is the birthplace of Japanese wine and the country’s largest wine region by production volume, vineyard area and number of wineries.

Why Japanese Wine, and Why Now?

Every year the Institute of Masters of Wine organises study tours to different regions. Past destinations have included Jerez in Spain, Uruguay and Peru, and the choice often falls on up-and-coming regions rather than famous appellations. Japanese wines and sake have been winning awards at international competitions, and interest in Japan within the Institute had been growing. This time, more than 100 people applied to take part. The tour was organised by Kenichi Ohashi MW, the first Japan-based Japanese national to become an MW. Ohashi MW pointed to two strengths of Koshu: its relatively low iron (Fe²⁺) content, which makes unpleasant flavours less likely when it is paired with raw fish, and its naturally lower alcohol level, which suits the current preference for lighter styles.

How Koshu Was Judged

Koshu is a grape variety native to Japan, with thick skins and good resistance to humidity. At Katsunuma Jozo, the MWs compared Koshu from three plots (Shimoiwasaki, Torii-hira and Isehara), all vinified in the same way. Sonal Holland MW, India’s first MW, rated the 2025 Isehara highly as a wine that can be enjoyed young yet also aged. Lisa Perrotti-Brown MW, former editor-in-chief of the US publication The Wine Advocate, tasted a 1957 Koshu at Grace Wine and said it convinced her that the variety can withstand long ageing. Fiona Morrison MW, a member of the family that owns Château Le Pin in Bordeaux, said that Japan is the only country succeeding with Koshu, and believes that having a variety found nowhere else in the world is a major asset in the international market.

Viticulture Shaped by a Rainy Country, and Bold Winemaking

What interested the MWs most were the techniques adapted to the wet climate. Katsunuma Jozo’s “kasa-kake” involves fitting each bunch with a small paper umbrella to protect it from rain and disease, which reduces the use of agrochemicals. Manns Wine presented its “rain cut” system, in which plastic film is stretched over the vines to keep the rain off. 98WINEs in Enzan showed an unusual approach: around one tenth of the grapes harvested for white wine are dried in the sun for about two weeks, then returned to the fermenting tank.

In Europe, too, a growing number of wine shops and Japanese restaurants list Koshu. Start by pairing a young Koshu with sashimi, carpaccio or grilled white fish, and notice its lightness and restrained aroma. Then try Koshu that has been barrel-fermented or aged, and you may sense the difference in depth that the MWs discussed. On the label, look for the vineyard or plot name as well as the producer. According to Morrison MW, the impressions from this visit will spread to sommeliers in many countries through social media. Before long, you may well see Koshu appear on your local wine list more often.