Rika Sawaguchi is the energetic high school student who serves as the human advisor to the detective agency founded by Norakuro and his grandfather, Norayama Kuroyoshi. She lives next door to the Kinoshita family in Suganami, Tokyo. Norayama recruits her shortly after renting the second floor of the Kinoshitas' apartment for their detective office, bringing her into the agency from its very inception.

Her advisory role becomes active by the agency's third day, coinciding with their first case. Her presence immediately creates a striking impact, causing a surprised and flustered reaction from Norayama that mirrors a notable scene from Dragon Ball where Yamcha encounters Bulma.

Beyond detective work, one episode titled "Rika-chan's Lover Selection!" centers on her personal life and a romantic decision she must make.