There is alternative login method in Devil Book called Link code.
■ Account Link
① Tap the 'Menu' Icon.
② Tap on 'Option' (Cog Icon).
③ Tap the area shown. It will show your Link Information. Link Information includes an ID and a code to identify the account data.
④ Confirm your account ID and the code.
※ These codes are unique assigned numbers to identify an account.
Therefore, please do not share them with others to secure your account.
You can play Devil Book through your account ID and Code.
⑤ Tap 'Change the Account' at the log in screen.
⑥ Tap on 'Link Account' at the bottom.
⑦ Enter the Account ID that you have previously confirmed.
⑧ Enter the Account Code that you have previously confirmed.
⑨ Tap 'Link' to complete the account link.
Please note that you can log in to other devices using that same ID and Code.
※ The guide was produced in a separate test environment.
So, It may change depending on the update and development situation.
Thank you for your love and interest in the Devil Book~
Devil Book Team