How to get Japanese Google Play for Renta app?

I recently bought a book on Renta, and wanted to have their app to use offline (this).
However, I’m having trouble getting the Japanese Google Play to work. I’ve tried VPN/new account etc… I’ve also looked around for more guides, but all the ones I saw didn’t seem to work for me and were relatively old anyway (which made me unsure if it was just my incompetence or if they actually didn’t work anymore).
Does anyone know how to get the JP Google Play? Or anyone got that app and can tell me how they did it? I’m not going to be spending money on there or anything - I just want that one book reader app.

Thanks!

EDIT: I managed to get it to work! I changed some of the settings in Tunnelbear (before I hadn’t been able to open the store properly with it on) then I made ANOTHER new account (Settings>Account>Add Account>Google) with Tunnelbear still on, opened the play site and was able to download the app.
Exactly the same thing I’d done before, but I had a different setting clicked on the Tunnelbear which I’m guessing is what made it work.

Do you have AdWords or AdSense associated to your Google account? That kind of accounts cannot change country.

I don’t think so? Honestly I haven’t heard of that before, complete noob at all this. I did try making new accounts (as some guides specified) and those ones didn’t work either.