To register via SMS, select "SMS," choose "Japan" for "Country/Region," enter your phone number, and click "Receive code via SMS." To register via voice call, select "Voice call," choose "Japan" for "Country/Region," enter your phone number, and click "Receive code via voice call." (When "Voice call" is selected, an extension field will be displayed; please leave this field blank.)
[If you do not receive the authentication SMS (Short Message)]
Spam filters or "Unknown Sender Screening" features may be enabled.
Please refer to the manual provided by your carrier and check your settings.
・Docomo(日本語/Japanese)
https://www.docomo.ne.jp/info/spam_mail/sms/
・au (日本語/Japanese)
https://www.au.com/mobile/service/sms/filter/
・Softbank(日本語/Japanese)
https://www.softbank.jp/mobile/support/mail/antispam/mms/