While there are many ways of making a highball even in Japan, each bar has its own codified way to produce the drink—which all bartenders must follow. This is the method practiced at a small sake (and whiskey) bar in Ishikawa prefecture called Washu Bar Engawa. Perhaps you couldn’t distinguish it in a blind taste test, but the precise choreography certainly adds to the pleasure of ordering one of these highballs.
At Engawa, this is always made with a bottle of Suntory Kakubin, which is ubiquitous in Japan, but unavailable in the U.S.; substitute any Japanese whisky or blended scotch. In Japan, as elsewhere, a highball is often garnished with lemon, but Engawa’s proprietor insists on serving it un-garnished.