Mutekiya (literally "no-enemies shop" or "shop without rivals") is located in Ikebukero on Meiji Dori south of the east entrance(s) to JR Ikebukero Station, and further south of some of the Seibu stores and Muji. It had fairly long lines for a Friday afternoon - tourists might have an advantage here since if they come during the week they will avoid the unbelievably long lines that are supposed to be present on the weekends. Also watch all of the bicycles that zoom down Meiji-dori, both on the street and on the sidewalks. There are no seats (for waiting) inside, you will be motioned to come in by the staff when seats are available, either at the counter or one of the small tables. Watch the first step when you go in, it's right next to the register and someone managed to trip over it when I was there. Note the interesting woks hanging outside, painted with the store's name in kanji. I had the chashu-men, which is not on the English web site but was on the Japanese menu that the staff had when they came out to take my orders ahead of time - be ready with what you want to order ahead of time - you could print out the English menu from the link below and circle what you want and bring it with you. The chashu was of medium thickness and well cooked - the soup was a really really creamy tonkotsu that must have been strained multiple times. The noodles were just plain. All in all it was good but not sure it's was worth waiting on line 40 mins for.
Shop home page (note the helpful "Foreign Langurage" link in upper right)