Who knew Japanese wine could be this good? A master sommelier describes it as having "an elegant acidity and fruitiness. Later you get a slow rush of umami." Explore the secrets of a Japanese wine served on international first-class flights. It's made by sumo fan and single mother Saito Mayu, who's braced to tackle the world. We follow her small winery in Koshu, Yamanashi Prefecture from summer to winter. Discover why its wine is taking the world by storm.