Japan, in contrast to the rest of the world, still has a fairly healthy CD sales market (last year 85% of music sales in Japan were CDs). It is definitely shrinking (17% 2014), but still accounts for a significant portion of world wide CD sales (Japan is still the second largest music market world wide).
The reasons are probably multiple, a mixture of the demographic (older people buy more CDs), the collectable fandom culture and finally the lack of streaming options. The last point in particular is interesting since no streaming service, domestic or foreign, have ever really caught on in Japan. In fact, most of the global services have never even been introduced here.
They are the perfect waterhole to batch sample new music regardless of genre, as they usually carry a very wide selection. Whenever I go to Japan I like to stop buy and rent a bunch of discs from artists or genres that interest me, and then pick out the stuff that’s good enough for keeping.
If you visit Japan, don’t miss out on this opportunity to listen in on what’s currently popular.