You can remove them on the au ID Membership Information Site.
Please see below for detailed instructions.
Access the au ID Membership Information Site and log in with your au ID and password.
Check the devices (such as mobile phones or computers) that you want to remove.
Tap on "Deactivate Verification" [認証解除].
After confirming the displayed content, tap on "Deactivate" [解除する].
The process has been completed.
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