Across from the Shinjuku station Yodobashi Nishi Guchi Tokei Kan (watch store) - where I was getting my wife's watch battery replaced, is Xi'an. It has some of the hottest and most flavorful toshoumen anywhere. It's on the fourth floor in one of the these crazy Sega game buildings. When I got there it was about 1/2 full at 2 PM, and the floors were sort of dark. Many of the wait staff spoke both Chinese and Japanese. Unfortunately you don't get to see them slice the noodles up by hand into the pot (from a block of dough) from the non-smoking section. I ordered the ra-yu-su-ran-men, a form of toshoumen and suratanmen combined - very slippery and rich noodles, lots of ground beef and ra-yu in the broth - definitely good to the last drop, with sesame seeds too. The combination of the ra-yu and the added vinegar gives it the type of taste and smell that can easily overwhelm your nose and tongue - be careful. For another 500 yen you can get a plate of 8 good-sized gyoza with a dipping sauce. However these gyoza have a fairly light taste, not strong, and they was more filler in the filling than meat. However they might be good to dump into the soup, the sauce that came with them was good but not spectacular. They will bring you a special bib and there is a pitcher of water at your seat. The portion was decently-sized for the price and there was an option for omori. Take a look at the regular dinner menu also - several delicious-looking things there including a togarashi chicken and black vinegar pork spare ribs.