if your devise is android, there is a way to use SD card as a internal storage. that will increase your storage space, but you need to format your device. anyway, my caravan stories app seems to take only 3.5GB, so reinstalling app MAY be worth to try. (don't forget to link your account before uninstalling if you try.)

the game is tied to the site, did the reinstallation of the game, how do I log into my account?

press the left button?

go to masters site, find "設定"→"ゲームデータ引継ぎ"→"引継ぎコードを発行する". you will receive a code number on Email, then launch caravan stories and go back to your image, and press the right button (not left). enter the code number you got in the field. the download will start.

ご協力いただきありがとうございます:)

reinstalling the game freed up 3 Gb

my pleasure. good for you :)