How to remove your Osu account
Sorry, no removal here, as was answered on their forum: it will leave holes in the database (LOL?). You may request to deactivate your account at http://osu.ppy.sh/forum/5
Helpful Trick: Obfuscate your profile info.
Because most accounts and profiles at Osu cannot be removed, we suggest you login and change your account and profile information altogether.
Make sure you are logged in to your account on the site and click on the profile or options settings. Locate the fields with your personal info (email, name, address) and fill in generic, random information instead. If you can only select from several fields, change anything personally identifying. If possible, use a homepage/URL field or long text field (such as Description) and put this line in it: http://remove.org/removal-requested. This may encourage webmasters and admins to create an easier removal outlet.
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for Osu using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Osu. Click here to find out how.