Matsuya is one of the fast food chains in Japan that specializes in gyudon. Apparently this is a popular lunch option for salarymen who want to come in, have a quick lunch and then get back to work. Another similar chain that specializes in gyudon is Yoshinoya. Gyudon is a Japanese dish that is literally a bowl of beef (gyu) on rice (don). The beef comes in thin slices and is usually cooked with onions in a mildly sweet soy sauce. As with many other quick service restaurants, you order at a vending machine and then when there is a free seat at the counter, you sit down and hand over your order ticket to the server. There is water, utensils and a small variety of condiments on the counter for you to serve yourself.
I had the most basic bowl which was the beef with onions on rice and it also came with miso soup. I found the beef to be very tender and mildly fatty. Similar to what you would use in hotpot. You can also get the bowl in different sizes as well. It was quite delicious considering it was so simple!