Introduced halfway through the manga and the first season, Reika is Nogami_Saeko's younger sister.

She runs the "RN Detective Agency" (RN being her initials), right next to Saeba_Ryou's apartment. She worked in the Tokyo Police Department, like her sister Saeko, before becoming a detective.

She's as manipulative as her older sister Saeko using her charms on Ryou. On the opposite to her "lawful" sister, who despite the fact they're as much as manipulative as the other, Reika being also a P.I. will never miss a chance to make profits whatever case she's given. But she's still goodhearted and will do charitable/good actions if the context pushes her to do so.