Not sure if anyone has mentioned this elsewhere, but there's a chain of Indian Vegetarian restaurants called Nataraj. I know they have at least 3 locations, one in Ginza (7f in the building across from Matsuzakaya on the main road), one in Ogikubo (it's close to the station, downstairs in a basement floor), and another.
Really good all-you-can-eat buffet lunch for 1050 yen. Love it!