On the morning of Nov. 3, the line leading to the entrance of Hibiya Park snaked along the sidewalk and coiled around the corner, several meters from the gate. I was there for the Yamanashi Nouveau wine festival but had assumed that the throngs had come for some other purpose. It was a moment of cognitive dissonance: That there could be so many fans of Japanese wine was a proposition my brain found difficult to accept.

The popularity of the Yamanashi Nouveau fair, which started in 1987, has grown over the last few years. According to the Yamanashi Prefecture Winemakers Association, 5,300 people turned out for last year's one-day event in Tokyo (there are also legs in Osaka and of course Yamanashi). This year, the organizers turned the festival into a two-day affair. By the time I left, around 1:30 p.m., over 5,000 people had already entered the venue.

Until recently, serious wine drinkers have regarded Japanese wine as little more than grape juice with a kick. But quality has improved, and wineries producing sophisticated styles are popping up all over the country. Rica Miura, a wine advisor with the Japan Sommelier Association, attributes the improvements to the fact that the new generation of winemakers has studied enology and viticulture overseas.