Backup
App::
Backup app and data using your favorite backup tool (example: Titanium Backup)

Saves:
- Might need root
Use your favorite file explorer (example: X-plore File Manager)
Go to /data/data/jp.co.hit_point.nekoatsume/files/
Copy /data/data/jp.co.hit_point.nekoatsume/files/savedata_system.sav (might be different for Amazon version) to another location (preferably not on your device)
You can try to copy it with adb also

Recover from an app that refuses start
- If you're rooted:
First backup the app and data (if applicable, ensure that your max backup count is high enough so your new backup won't erase latest one) using "Backup App" method upper in this page.
Then backup your saves using "Backup Saves" method upper in this page.
If you have an older backup, uninstall game and restore an older version. If not, download older version from this site. Finally restore game save either via a backup app or by copying it back.
- If you're not rooted:
Either root your phone, or wait for the next update that will (hopefully) solve the problem.
You can also try to backup your save file by using the Backup Saves method upper in this page. If you succed, simply uninstall the game, install older version (download available from this site) then copy back your backed up save file.
- Anyway, DO NOT UNINSTALL APP, or you will lose all your progress.

Backup / restore without root: https://play.google.com/store/apps/details?id=com.koushikdutta.backup