Board Thread:Touken Ranbu Pocket/@comment-4214488-20160401021830/@comment-26044227-20160401045247

Are you still able to open the app?

If so:

When it loads to the start screen, click the blue button in the right-hand side. Click the button under the phone -> phone picture, then copy down the ID/password that you get. Uninstall the app, reinstall it, then resync your freshly installed app with that ID/password.