In restaurants in Europe, America, and other places, guests pay a tip as a kind of service charge, but there is no custom of tipping in Japan. Some eating and drinking establishments take a service charge, but in general such charges are included in the overall prices and in the total amount you pay. So, don't leave any tip. If you leave money quietly on the table as a thank-you for good service, you will cause a panic and might have staff running after you to give you the money back, saying that you forgot it on the table. So, if you want to express your appreciation for good service, instead of giving a tip, it is enough to try to communicate your thanks to the staff in other ways, perhaps with a smile.