With the proliferation of bars and restaurants serving decent nihonshu, there is no need to make a big deal out of searching for a "proper" sake pub. Dotted throughout the sprawling underground shopping areas that lie below many of the major stations in Japan are little sake havens. Take, for example, the easily accessible and oft-passed spots in Tokyo Station's immediate environs.
One recommended shop is Keyaki, which is inside the wickets, downstairs near the Yaesu Central Underground Exit, close to the Gin-no-suzu waiting areas. In a slightly upmarket setting, Keyaki serves fresh seafood-centered set meals and a good range of izakaya food. The draft beer comes in glasses with finger indents for proper gripping, which somehow makes the beer taste significantly better.
But the several selections of sake are what makes it worth stopping in for. Most notable are Goshun, Kubota, Denshu, Kokuryu and -- get this -- six types of Juyondai, ranging from 650 yen to 2,500 yen a glass (the 850 yen Funadare will do you just fine, but the Honmaru honjozo is great for 650 yen). Keyaki, (03) 3214-6161, has shops all over the Tokyo Station area, but this is the one you want -- and you won't even have to exit the wickets.