Okay, so since the release of the app is pretty soon, I'm sure everyone wants to download it and might not be able to because it might be only available to Japan. I'm sure it'll be easy for Apple phone users since they can change the region in itunes, however, it might be a little more confusing for android users.
There's an app called Qooapp and you can either google it to download or get it straight from the Google play store! It's safe, though it is in chinese. You can simply search up Touken Ranbu or the japanese name in the app and you can download from there. Since it's from a separate store, you'll get a notification from your phone to allow the download of Tkrb pocket from an unknown source. Make sure it says something like "allow for this installation only" and you should be fine - virus free!
Hopefully, this'll help you guys out! :D