Ryoko Negishi, known as Ryoko, is an 18-year-old investigator dedicated to finding "The Lost." Following her father's path, she serves as both a detective and police officer. She possesses long, burnt orange hair typically secured in a ponytail and striking indigo eyes. Her consistent attire is a forest green suit paired with matching shoes, complemented by a distinctive Queen of spades tattoo on her thigh.

On duty, Ryoko exhibits a focused and astute personality, demonstrating notable skill in identifying threats. Away from investigations, she reveals a softer, compassionate nature. Her professional pursuits center on exposing a mysterious organization called The Agency.

This mission culminates in June 2019 when Ryoko uncovers her 22-year-old colleague, Shunpei Aoyama, as an Agency affiliate. Immediately following this discovery, Aoyama fatally stabs her, abruptly ending her investigation into The Lost.