To get Windows 8 / RT apps, only way is to go, find, and install from Windows Store (except if you are developer). By default, Apps listed are filtered by language you use.
If you think Apps are still few in Windows 8/RT, you can change settings to remove language filtering.
Let’s check with Utility for example. For utility, there’s only 10 apps for Top paid (in japan).
Open charm, click settings.
Set “Make it easier to find apps in my preferred languages” to “No”.
This will (slightly) increase number of Apps listed.
By changing Windows OS language setting, Weather, News, Apps, and other items change. You should try and see for fun.
This post is also available in: Japanese