I'm sure with a quick google search you may find if there are any dog parks in Japan
Also:
Top 10 Dog Friendly Cities in Japan
Also, a bit off-topic, but some vets prefer that you dress your animals if they have short fut, especially in the winter or in colder climates. Unnatural, yes. Cruel? Hardly. Dressing an animal up doesn't make it any more or less happier - if it loves it's owner and life, it's not going to give two thoughts over what's on it's back.
Plus, if you live in America like I do, you would see that it would be impossible to NOT buy things that were made in China.