Originally just a small counter shop serving udon noodles, Nanakura has since grown into a full-sized, very lively after-work izakaya with a focus on fresh seafood. The excellent, rather unique udon is still a big draw though, and worth a special trip on its own. The noodles here are cut much thinner than average, and are served with a rich, fatty, and amazingly tasty duck-based dipping sauce.
A bowl of noodles will set you back Y1080-1480 depending on the size, but if you have the time it's worth checking out the rest of the menu. Charcoal-seared katsuo tataki (Y950) is a stand-out, as is the sake-marinated grilled otoro tuna (Y1260). There's a small but serviceable sake selection, and of course beer and shochu cocktails. Budget around Y3500-4500 in the evening, or less if you just want a bowl of udon.
This book will introduce you to more than twenty of Japan's favorite specialty foods that are less well known abroad, along with a guide to the best places in Tokyo to try them and expert tips on what to order. From Bento.com.