Take up golf.
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
Take up golf.
It's funny, I've heard that golf is prohibitively expensive in Japan, to the point where some Japanese buy clubs, carry them around, maybe go to a driving range occasionally, but never actually get to play on a course.
So taking up golf might be even more frustrating to the OP than servicing his regulator!
Japan is not a DIY culture country, they nearly always call in the so-called "professional" for what we'd consider to be very simple repairs and maintenance, whether that be in the home, on the car, SCUBA gear, etc.. So the government of Tokyo prefecture doesn't care about a few foreign divers who want to service their own gear, the compressed gas laws weren't put into place with that in consideration. Similarly annoying to divers, we also have very strict knife laws, so if you're carrying any knife over 6cm then it needs to be for an obvious purpose (like fishing, diving, etc. and accompanied by appropriate sport gear) or you'll land a quick trip to a detention center.
.
So, there goes Japan on my crap country list!As a foreigner, in 7 years, I have been "inspected" a couple of times (you can't refuse if you're not a Japanese citizen). It's very uncommon if you look normal and aren't in troubled neighborhoods, but it's one of the lowest crime-rate countries in the world with a fairly closed immigration policy, so sometimes police are bored and randomly pick on foreigners. I get pissed when I see them blatantly doing this but complaining falls on totally deaf ears. I'd be more comfortable carrying a tank in a rental car rather than the small risk on the train because you never know when you're going to run into the next bored cop.
That many people in that small of an area you are going to need rules and cultural norms to restrict free will otherwise chaos will happen.
Look at almost any big city in the world you will find a similar situation.
To the OP I think that getting a small cylinder for home use and smuggling it home may be your best bet keep in mind that you shouldnt need that much air to test and tune your regs.