When Kyoichiro comes home, he hears that his 14-year-old son Kyosuke was stabbed to death. The person who killed Kyosuke turns out to be 13-year-old Mitsuru. The two boys were classmates. Due to Japan's juvenile law, Mitsuru will not receive commensurate punishment for his crime. Kyoichiro points his anger at Mitsuru and his mother Hatsumi, but Kyoichiro sees that Hatsumi also suffers from her son's actions.
Kitagawa Keiko plays Sasaki Rena, a detective who risks her life investigating detectives for her dead sister. Beautiful, intelligent, and with a great memory, the talented woman judges situations and chooses the most appropriate course of action. Her brutal past surrounding her sister's death inspires her to learn everything she can about detectives, leading her to visit the Suma Research Company. As the sole member of the Anti-Detective Department responsible for investigating and pursuing unethical detectives, she is a solitary lady detective.