Waltz, a tiny standing bar that specializes in natural wines, is nearly impossible to find the first time you try looking for it. On a recent Saturday evening, the bar's obscure location — on a dimly lit backstreet between Tokyo's Ebisu and Shirokane neighborhoods — confounded me and two of my friends, as well as the GPS function on my cellphone. Waltz's service info lists no phone number, probably because the bar fills up so quickly that owner Yasuhiro Ooyama has little time to field calls from lost customers. By the time we arrived, the watering hole, which can fit around 10 guests, was already packed with regulars sipping glasses of unfiltered vin naturel in various hues and nibbling on homemade charcuterie — and the doors had only been open for 20 minutes. At 6:30 p.m., Ooyama began turning customers away.