Tsuru Dontan BIS TOKYO Marunouchi is a fusion udon shop in Marunouchi, connected to the underground passage at Tokyo Station. It serves carbonara udon and sukiyaki udon along with inari sushi and eel sushi, and noodle portions can be adjusted free of charge from one to three servings in 0.5 increments. Ordering kiosks sit at the seats. Lines form from the morning, and entry takes about 20 to 35 minutes.