Fujidou Sayaka is the granddaughter of the famous detective Fujidou Souijirou. After her grandpa passed away, he stated that Sayaka can have his one million yen with the condition that she must work as a detective at her grandpa's agency. Or else, the money will go to the Tsurukamei organization.

Reiki, a 12-year-old boy who has been living with Sayaka's grandfather for 5 years, is now Sayaka's assistant. As pretty as Sayaka is, she's also very arrogant and doesn't like this job at all, and most importantly she often bickers over Reiki. One thing that they both didn't know at first place is that Reiki's innocent face is just grandpa's trick to seal Reiki's true personality - a cold and violent boy. And most importantly, the key to unlocking that secret turns out to be Sayaka's hot naked body!