Open 9am to 5am next morning (at least the one at Ikebukuro where we were). Excellent food and decent portions.
Try the hamburg (that's what they call a hamburger) with beef chops. Drop a portion of fries they server with good curry sauce and pay a small extra for all-you-can-drink soda bar and you'll be stuffed at a cost of some 1.500 yen, which is not bad by Japanese standards.
Favorite Dish: Hamburg with beef and Hamburg with grilled shrimps.