I found this article in English on a Japanese website that lists reasons why people should adopt instead of buying and talks about the problem in Japan of animals being abandoned.
RE: Japan- Appeal for Adopting Instead of Buying Pets
It was a good article that you linked to. I've never heard of crows eating newborn pups and kittens, but obviously it must happen. It's good advice that people should look into adopting from shelters instead of going to pet stores, unless the pet store carries pets from local adoption agencies, which many of the pet food places I shop do. We got one of our cats from a pet food chain store, but he was from a no-kill shelter and the agency people were there to interview each potential buyer first with a pretty intense information and question session. I think the adoption fee was only $100 and it included his being neutered. There was one time we bought a kitten from a pet store and she was sickly from the start and only lived until 7 years old, having died of kidney failure. I've since often heard pet store animals are not healthy and often come from kitten/puppy mills.
RE: Japan- Appeal for Adopting Instead of Buying Pets
I don't think there will be enough pets to go around if the only source is adoption. Soon there won't be any pets for adoption at all if this is the case. Most pet owners don't breed their pets. The population of pets will decrease dramatically if all "buying pets" are made illegal.