You can delete your account and all of its data directly in the app:
Everything: your profile, email address, activity history, palette and custom activities, friends and friend requests, blocks, reactions, and day summaries. There is no recovery. Combined world totals contain nothing that identifies you, so there is nothing to remove there.
One exception: reports. A report you filed, or one filed about you, is kept with a copy of the handles involved and of the reported account's display name and custom activity names, so deleting an account can't erase a report before it has been handled.
Email support@kuuluu.app from the address you signed up with and we'll delete the account for you within 30 days.