You can delete your account, and everything in it, yourself:
Everything in the account: your captures, tasks, projects, plans, memories, settings and devices, and your sign-in with our identity provider. You are signed out at once, and the data is removed from our database within minutes.
Our backups hold a copy until they expire, within seven days. After that, nothing you put in the account is kept.
If you signed in through another service, you can also remove Kelpie's access in that service's settings.