Namie is a young woman aged in her early twenties to her mid twenties. She has black hair which she wears down that sweeps all the way to the small of her back and has a fringe swept to one side of her face. Her expression is usually stoic or angry, and she has pale skin and brown eyes. She wears a typical long white coat and a light green turtleneck shirt that changes to a darker shade of green midway. For her bottom garment she wears a dark red skirt and black stockings.

She is the Chief of Yagiri Pharmaceuticals and sister of Seiji Yagiri. She harbors feelings for her brother. She is behind the recent human hunting in Ikebukuro which involves kidnapping people whose disappearances would not be noticed for unknown experiments. She seems to rely on Shinra for some tasks, including keeping their secret. She doesn't like the fact that Seiji is in love with Celty's head. She wants to get rid of what she calls "that thing." After Yagiri Pharmaceuticals ends up merging with another company, she makes a deal with Izaya and becomes his secretary.

Namie Yagiri is portrayed throughout the show and manga as a very direct and strong woman - she works hard to get what she wants, and no matter what, she will get it. Her personality is seen as very demanding, only ever showing kindness and sweetness to her little brother (due to her having a complex for him).