Yako Katsuragi

Yako is a 16-year-old high school girl and the very first character introduced in the manga. She meets Neuro when he appears and desecrates her father's shrine while promising to help solve the mystery of her father's death. This meeting quickly leads to a partnership: Yako becomes Neuro's cover, pretending to be an investigator while Neuro acts as her assistant.

She has an insatiable appetite (which people often associate her with) -with a cast-iron stomach to match- and a knack for understanding human psychology that occasionally provides Neuro with the information he is unable to obtain because he is unfamiliar with how humans operate. Yako is even able to understand Neuro, to a degree, thanks to an amalgamation between the two aforementioned traits; she compares Neuro's opinion of food (puzzles) over that for oxygen (shouki) to an experience that she had (hunting for oysters underwater). Neuro enjoys abusing her, though he does compliment her at times of success, albeit through a patronizing tone.

Despite all that Yako goes through on a daily basis, she is relatively calm during high-stress situations, such as being kidnapped by Sai. While her time with Neuro has definitely been a factor in this, it is left to question if Yako had this trait before she became Neuro's front. It is also notable that Yako's abilities, and potential, as an actual detective are shown to be growing over the series, starting with the Aya Asia case, albeit differently between both the anime and the manga.