We dropped by the Iseya restaurant in Kichijoji, Tokyo. It is located on the Kichijoji exit of the Inogashira park that also includes the Ghibli Museum, so you might find yourself visiting a location closer to this restaurant than you would think.
It is a yakitori and sukiyaki restaurant and the grilled chicken is great with a couple of cold draught beers. The place is dirty and full of character and the patrons are a nice mix of Japanese society. Quite different from most of the restaurants a tourist usually ends up in and therefore heartily recommended. Personally I love these kind of gritty places, I prefer to visit a salarymen lair above another one of those chain restaurants you find everywhere. See here for more details.