De "Malpedia" do exterminate-it.com :
PlaySushi Uninstallation
PlaySushi software usually uninstalls using standard Windows Add or Remove Programs functionality. However, if you was not able to remove PlaySushi by the normal way, please try the following steps:
Download latest PlaySushi Uninstaller from the following location: http://www.playsushi.com/Remove.ps
Run PlaySushi Uninstaller and follow instructions (Click “Next” on first dialog window and then “Reboot” on second). Your PC should reboot after that.
After reboot PlaySushi software should be completely removed from your system.
O mesmo link fornece muitas informações para remover manualmente o "Adware" do PlaySushi, espero que ele te ajude.