The smoking age in Japan is 20 (so is drinking), and from what I've heard from friends that have studied abroad, they really do enforce it strictly. Really, if your a tourist especially, I would stick by the laws. A lot of countries are far more stricter in there laws and penalties (very much so compared to here in the U.S.).

Most people though will smoke Marlboros (from my understanding though, that is Asia in general). You may come across DunHills and Cohibas too.

Women are the worse though in Japan when it comes to smoking. It's kind of a social click there.

The best thing I'd say for you though, if your 15, quit now; and wait till your legal age. Trust me, it's a lot more fun being able to buy them yourself, than to con someone into buying them for you.

I'm only saving up right now. I'm not going to Japan until I'm legal.