Your pixiv ID can be changed using the following procedure.
※ pixiv ID can only be changed only once for each account.
After changing your pixiv ID, returning to your previous ID or creating a new account with your previous pixiv ID is not allowed.
※ User ID (the numerical section of https://www.pixiv.net/users/○○○○○○○) cannot be changed.
For pixiv.me users
If pixiv ID is changed then the pixiv.me URL is changed, the URL prior to the change breaks the link.
Please be careful of the old URL posted on other websites.
■ Computer Version
You can change your pixiv ID from the User Settings page.
■ Smartphone Version
Your pixiv ID can be changed from the Settings on the left menu.