Just starting out with Android development; have a Nexus 5 bought in Japan, but with English version of android (presumably shouldn't matter). I installed Android Studio on Windows 8.1 to try making an app, but now I don't see my phone under "Choose Device". I've enabled developer mode and selected 'USB debugging'. Is there something else I need to do to get Android Studio to see my connected device?
Have you installed drivers for the phone? http://developer.android.com/sdk/win-usb.html
It appears that the the sdk does not "install" the USB drivers. You can select that usb drivers in the sdk to see the file location, open that up, and right click to install the driver yourself.