On the login screen, click the [Forgot Email/Password?] button at the bottom.

Click the [I Forgot My Email Address] button.

Enter the mobile phone number you registered with and click [Get Verification Code]. A verification code will be sent via SMS.
After entering the verification code, click the [Complete] button.

You will be able to see the registered email address!

On the login screen, click the [Forgot Email/Password?] button at the bottom.

Click the [I Forgot My Password] button.

Enter the email address or mobile phone number you registered with and click [Get Verification Code]. A verification code will be sent via SMS.
After entering the verification code, click the [Complete] button.

A temporary password has been sent to your registered email address. Please log in with the temporary password!
