(!!!) NOTE: account deletion is NOT the same as subscription cancellation or progress reset; by deleting your Yousician account you will lose all progress, information, followers and will be removed from the in-game leaderboards.
Click "Edit profile" and the profile page will open in your default browser. You will then see the "Edit Account" button below your Account Information:
At the bottom of the next page you will be able to delete your account:
It is not possible to revert any changes after you confirm the deletion.
Remember that you can access the same account from different devices. If you are using an Android version of Yousician and would like to change your username or email, simply install Yousician standalone on your Mac, PC or Linux machine to access the feature.