A mysterious organization keeps sending intimidating letters to Fiasse Christella, the principal of British Christella Music Academy. The purpose is to find the whereabouts of Fiasse's inheritance.
Although Fiasse already has a bodyguard, Ellis McGaren, she asked her childhood friends, the brother and sister Takamachi Kyoya and Miyuki to help Ellis. This of course is received by Ellis, as a professional bodyguard, with a cold shoulder.
Kyoya remembered an incident that was happened several years ago, when he was about ten years old. This incident was actually aimed at Fiasse's father, senator Albert Christella. So, is Fiasse's fate and case related to this past incident?