CB and ham radio in Japan

I wonder if someone could explain me some background about CB and ham radio in Japan.

I love doing CB radio from my car in my home country, and was wondering how difficult it is here in Japan.

If I understood correctly CB radio in Japan is heavily restricted to 9 channels AM with 0.5W. External antennas are illegal, basically ruling out any mobile operation from a car. Nevertheless you find a lot of second hand US CB radios for sale online and many trucks have antennas installed. There's also quite some chatter going on on several channels.

How do the authorities deal with this? Do they ignore it because it's an outdated technology and no one cares? Also, isn't CB radio about to lose it's legal license?

To keep my hobby alive I was thinking about getting a amateur radio license, but it seems taking the test and getting a license is only possible for Japanese nationals.

Any ham or CB radio enthusiast who could help me answer some of these questions?