This udon store, Kameya, is one of the many small stores that make up Omoide-yokocho (思い出横丁), a alley near Shinjuku Station. Omoide-yokocho literally translates to "Memory Lane," although I've heard it being called worse.
It's not the cleanest place on earth, that's for sure. But this small corner of Shinjuku is like stepping back to the 1950s and for that reason it is quite popular with many locals. People would drop by here after a Nomikai, to either continue drinking into the night or to finish the night off with a bowl of noodles.
Which is just what my co-workers and I did one night. Not sure how it usually tastes, but the udon was absolutely delicious at 2 a.m.