Board Thread:Questions and Answers/@comment-29724961-20171104171718/@comment-33611528-20171129212848

There's no way to move your save the file as far as I know, but people outside of Japan can get the Japanese version of IOS. There are two methods for this: If you're like me and downloaded Battle Cats when the half-translated JP version was released on the American App Store a couple of years ago, you can download that version through your "purchases" menu in the Updates tab of the App Store.

OR, if you're not me, you can make a new iTunes account with its region set as Japan. Whenever you log into the account, you'll be able to access the JP App Store and visit BCJP's store page (which has been removed from the English store ever since BCEN was released)

Sadly, there is no other language you can change except for English and JP.