While Tokyo is generally a pet-friendly city (with some stores actually welcoming pets), there remains a number of apartment buildings that won’t allow pets to be kept. Dogs of all sizes tend to be the most common Japanese pet, with cats in a somewhat distant second. There are a number of pet stores scattered throughout the city, and puppies and kittens tend to run well upwards of US$1,000 per animal. The high cost of purchasing a pet has prompted at least some within the expat community to either adopt strays or to reach out to ARK (Animal Refuge Kansai) which is an NGO based in Tokyo and Osaka that rescues abused or stray animals and finds new homes for them (http://www.arkbark.net/).
The rules for owning a pet in Tokyo are relatively simple and are almost exclusively targeted at dog owners. Indeed, dog owners must register their dog once it becomes 91 days old, and the dog must always wear a collar with its license and completion of rabies vaccination affixed. When outdoors, dogs must be kept in a cage or on a leash.
But beyond this, animal lovers and their pets are generally free to go wherever they want. Most parks welcome animals, and there are a variety of open air restaurants that also allow pets to join their human companions for a meal.