三田製麺所 / Mita Seimen is a chain of tsukemen restaurants with many locations in Tokyo and even some overseas. The main shop is not far from where I live, near Tamachi station.
Tsukemen occupy a middle ground between ramen and abura soba; while there is soup, it's served separately from the noodles, and depending on the type may be too thick to drink comfortably on its own. The noodles are thick like abura soba and are usually served cold, and you dip them in the sauce before eating. Most restaurants (including Mita Seimen) can thin the soup for you after you finish the noodles if you'd like to drink it.
When I went by one of the special flavors was the sanshou noodles, so I gave that a go. It tasted like a bowl of savory lava, which is even better than I was hoping for.
The portion here is "normal", the smallest portion, 200g of noodles. You can get up to 400g without paying extra. You can also pay a little extra for toppings or extra meat in the soup.
The main shop is right next to my usual mahjong parlor and open late, so I'll be going back. While the top page is an annoying Flash mess, the shop pages on their site clearly show the times and menus of each location, so give it a look. Ψ