Apart from the language, there is another good reason for some restaurants to not want serve tourists: turnover. A friend mine went on a trip with 3 friends, they were refused service in quite a few places because, when seated at a counter (not a table), they will take the space of 4 individuals. They have dinner and drinks for 2-3 hours and during that time the restaurant could turn over those 4 seats perhaps 3-4 times, meaning 12-16 individual meals by single, japanese patrons coming in and out for a quick meal...