Chaebol heir Jin I Su, who accidentally became a detective but discovered his calling and a strong sense of camaraderie along the way, returns to Violent Crimes Unit 1 after completing official training at the police academy. However, when Ju Hye Ra, the "devil instructor" who tormented him during his academy days, is appointed as the new team leader, a chaotic partnership begins to unfold. Jin I Su is a playful and carefree third-generation chaebol heir who became a parachuted-in detective. He is a young, wealthy, and unconventional investigator who mobilizes not only his family's immense wealth and connections but also his quick wit and the various skills he picked up while goofing around to take down criminals. Ju Hye Ra is a former ace of the National Police Agency's counter-terrorism team who volunteers to become the new leader of Violent Crimes Unit 1, making her Jin I Su's direct superior.