I don’t have a VPN installed, though I did have Tokyo/Osaka time zone active on my phone (the Mobage HiguUmi Card Battle app needs it to work properly) but I doubt that would affect anything.
I can guarantee that it’s possible to download through the Mobage app service, without a VPN.
I received a chat message from the Mobage app with a link, which took me to the ABOW Mobage listing. I followed the link and there’s an option to download the game. (After clicking the option button, I was taken to my primary web browser where the app began to download automatically.)
EDIT: I’m pretty sure that you can’t download from the Play store or directly from the ABOW website without some VPN, but if you have the Mobage app you should be able to get it from there without problems. If it doesn’t let me know and I can investigate it