I ride road bikes a lot and frequent a number of different stores for parts and ideas. The best serious bike shop chain in Japan is Y's Road ("wise road"). A quick search for a Trek 520 at their website yielded this page, which is a store in Osaka. Generally I've found that if one Y's Road store has a bike model in stock that you want, they can get it to a store closer to you, for you to look at, in a couple of days. But then the pressure is on to buy it...!