Sambo is a gyudon restaurant in Akihabara, Tokyo, known as a Steins;Gate pilgrimage spot. The menu has only gyudon, with the meat served either on top of the rice or on a separate plate. You buy a meal ticket from the vending machine at the entrance, sit down, and the food arrives almost immediately. Customers eat and leave, and ordering from the ticket machine is confusing for beginners in Japanese.