Nakano isn't necessarily regarded as a neighbourhood that you travel to for food - most restaurants here are filled with locals, or those stopping off on their eay to destinations further west. The exception is Maguro Mart, a veritable bonanza of everything tuna. What people come here for is nakaochi, or raw tuna served on the bone. You're given a spoon, and then simply scrape the meat off the bone until it's clean enough to be turned over, after which the fun starts again. With a decent-sized tuna serving six or more, it's a very popular option for groups of friends. Other menu items include a stunning set of sashimi, with rare cuts of tuna, and the maguro yukhoe, or tuna tartare. Consider ordering the course, which gets you six dishes including the sashimi set and the nakaochi, if in a larger group. The mindboggling thing is that all of this will probably set you back less than ￥5000.Note that getting a reservation takes quite a bit of perseverance (a fancy hotel concierge isn't of much help per se), as it's exceptionally popular. Reservations open a month in advance, with weekends/regular dining times often snapped up within minutes of the phone lines opening. There is also only a Japanese menu, and staff don't speak English - take a Japanese friend if you can.