You can delete your account from the Settings page.
https://sketch.pixiv.net/settings
After you delete it, you won't be able to access all of your data.
Please note that deleting your pixiv Sketch account will not affect your pixiv account.
Visit the following page to learn how to delete your pixiv account:
If you're using the pixiv Sketch app.
Android: You can delete your account from "Settings".
iOS: You cannot delete your account on the app. Please do so from desktop.
If you don't know your account information, please send us an inquiry.