You can check if you are registered with your email address or not by registering for a Yu ID as a new user.
[If you are not registered]
Email address: (Title: Initial registration is complete) will be sent.
* You can complete your registration from the URL in the email.
[If you are registered]
Email address: (Title: Initial registration has failed) will be sent.
You have a Yu ID registered with the provided email address. You can log in and use the service.
* If you forgot your login password, you can reset it.
＜To register＞
https://lp.jpid.pf.japanpost.jp/
＜To reset password＞
https://mypage.jpid.pf.japanpost.jp/password/reset/request
＜Related questions＞
Q. I registered for Yu ID, but I have not received the email necessary to complete the registration process
Q. How do I register for Yu ID?