Open Account, then Sign-in and security. Changing the email address or the password asks for the current password first.
When the email changes, we send a notice to the old address too. When the password changes, other devices are signed out.
How do I change my email or password?
Account → Sign-in and security. Both need the current password.
Was this what you needed? If not, contact us and a person will reply by email within one business day (Korea time).