When you walk in a residential area of Japan, you could see people walking dogs. The 3 most popular breeds of dogs in Japan are a toy poodle, chihuahua, and miniature dachshund (as of 2010). All of them are small. On the other hand, I found the most popular dogs in the U.S include a retriever, shepherd and terrier. They all are relatively big. This difference might come from the size of the houses of both countries. Besides, in Japan many apartments don’t allow the tenants to have big dogs. This may be another reason.
Anyway, Shiba dog is the most popular indigenous kind of dog in Japan. It is a frisky breed and loyal to the master. Shiba is characterized by its almond-shaped eyes and trundle tail.
The picture below is a very famous dog appearing in TV commercials of Softbank, a Japanese mobile phone carrier. Sooooo cute!! It is the breed of Hokkaido dog.(from Google images)