You can set it up through the au ID Membership Information site.
For details, please refer to the information below.
Access the au ID Membership Information Site and tap on "Log in by entering your au ID" [au IDを入力してログイン].
Enter your au ID and tap on "Next" [次へ].
Enter your password and tap on "Login" [ログイン].
Enter the verification code [確認コード] sent to the phone with the fingerprint authentication set up, and tap on "Next" [次へ].
Tap on "Next" [次へ].
"Biometric login setup" [生体認証によるログイン設定] is now completed.
Android: Android 7.0 or later and using Chrome browser
iOS: iOS 14.0 or later and using Safari
Has your problem been solved?