The secretive crime boss Oniyama keeps no records of his organization or business partners, leaving every vital detail locked in his head. Investigator Haruka therefore applies for a secretary position at his legitimate front company, planning to work her way into the criminal operation, become his direct subordinate, and extract the truth. Despite warnings that entering the enemy boss’s inner circle is reckless, she goes undercover and earns a place as both secretary and mistress, steadily gathering secrets. Three months into the mission, a chance to seize decisive evidence finally arrives—but something happens that night.