If you are travelling in Tokyo then you will want to try some of the local traditional grub. There is small man made island inside Tokyo Bay called Tsukishima ] filled with restaurants which serve a dish called Monjayaki (sometimes just called "Monja").
If you are going by public transport then just get off at Tsukishima station on the Tokyo Metro Yurakucho Line or Toei Oedo Line. Once you get off then just follow your nose!