Poppoya is a fairly small, very informal shop with several branches including the main original store in Nihonbashi, one in Suidobashi and a couple of others in Chuo-ku and Bunkyo-ku. (There is a well-known movie Poppoya with Ken Takakura, which is a very good movie, but it has nothing to do with ramen or this shop). This shop in Nihonbashi has less than 10 seats, no tables, and a relatively sweet strongly-flavored broth, with a large amount of onions, as though someone had taken regular Jiro shoyu tonkotsu, put a bunch of chopped up tama negis in it and let it simmer for a couple of hours, lots of suspended fat and onions, salty-oniony sweet taste. Veggies were almost completely moyashis. However the pork slices, while of good quality and fat level, were a disappointment in size, only two small ones (barely matchbook sized) for 150 yen. The noodle amount was a bit disappointing too however they were medium-sized and well-cooked. Extremely drab interior, however I would go back again for the broth and noodles (and get omori), especially the broth.
Foodpia Olive page (more pictures)
Diddlefinger Map (English labels)