This is a ramen exclusively for "one cup" that is offered only at night. It seems that the amount is smaller than usual and it is optimally finished after a drinking party.
You can order by presenting a receipt that shows that you ate or drank at a pub or restaurant on the day (not applicable to retail stores such as convenience stores, supermarkets, and liquor stores). Groups of 2 or more who ordered alcohol in the store can also order. The price is 500 yen (tax included).
The stores and service hours are as follows.
From 22:00 to closing Ebisu store, Yoyogi-Uehara store, Meidaimae store, Kichijoji store, Machida store, Kannai store, Matsumoto store, Sendai Aoba-dori store
From 20:00 to closing Shinjuku Island Tower store, Asakusa ROX / 3G store, Marunouchi, Toyosu store, Toyama store