Just inside the corner going right from the second light on the KFC street going south from the west exit of JR Shimbashi station is Atago. Hard to spot without the banners out in front, since it is just a black stone storefront with almost no visible sign. The map suggests that it is right on the corner when in fact it is in from the corner by one building. No markings on the building itself, unless they put out the big white banners. They had a wite plyer posted outside that advertised a new mazesoba dish sort of like the one at Miharu - more shoyu and oil than soup shiru. You will get a small dish of extra broth with it, and special ra-yu spicy oil to put into it to jazz it up - instead of the ra-yu I recommend the standard black pepper - and you'll have to be a bit generous with it. They also have a special yuzu soba, yuzu seems to be popular lately for tsukemen flavoring. You can see a picture of the evening menu here. They actually have two menus, one for hiru (lunch) and one for yoru (evening). It was a very smart spicy broth and the pork was pretty good. They also threw in a special goma-tamago, but I couldn't taste anything special over and above regular a regular yude tamago. There were lots of people coming in, the place has a a counter with 9 seats in two sections, and 2-3 tables. They have an English menu that they will come over and offer you. They also have an interesting mirror on the back wall that lets them see what you are doing behind the high counter. It's a dark black, not so well lit interior.
Livedoor Ramen page
Diddlefinger Map (English labels)