'''''' – The main character, an originally sixteen-year-old member of the Detective Shelf Collection (DSC) who becomes assistant to Kyoko Kirigiri, who is three years younger than her, writing of their experiences together in solving crimes. Having become a detective to find her sister's killer, Yui is killed in an explosion during the seventh volume. '''''' – The
title character, the future "Ultimate Detective" whose family have been detectives for generations. Seeking to return the Kirigiri name to its former position after being abandoned by her father following her mother's death to be raised by her grandfather, Kyoko meets her assistant Yui at 13-years-old, after being involved together in a murder case, the series following the pair over the course of the story. In the seventh volume, Kyoko has the flesh burned off of her hands while trying to rescue Yui from the aftermath of an explosion. '
– An elite detective of ambiguous morals known by the media as ', who specializes in
homicide, who was formerly assisted by
Polaris P. Polanski. In the second volume, Suisei is revealed to be
gay. '
– A male androgynous Triple-Zero Detective of the Detective Library introduced in the third volume of the series, commonly nicknamed '. '''''' – A rank-7 detective specializing in technological crime introduced in the third volume of the series. '''''' – Kyoko's paternal grandfather and adoptive parent, a master detective who trained his granddaughter in honing her detective skills. '''''' – Kyoko's maternal grandfather, a master of seven
Japanese martial arts who taught his granddaughter in
self-defense. '''''' – The
Headmaster of Hope's Peak Academy and Kyoko's estranged father, who abandoned her as a child. '''''' – A tall
European
assassin dressed as
Little Red Riding Hood who kills her targets by impersonating the
M.O. of local
serial killers in the corresponding country or state she is in, in particular
Genocide Jack. '''''' – A short
Romanian assassin in possession of a
private jet, which he uses to flee after publicly killing his targets with a
silenced pistol. '''''' – An assassin and former "Ultimate Rock Climber" of Hope's Peak Academy, capable of scaling walls with his bare hands and bending metal and bone, having previously illegally climbed
Angkor Watt and the
Eiffel Tower. '''''' – The "host" of the Duel Noir at the Norman Hotel. Supposedly modeled after a serial killer from roughly 50 years ago (likely a reference to
Norman Bates), he only appears as a painting shown on a video screen in pre-recorded messages. '''''' – The "Ultimate Lucky Student" of Hope's Peak Academy and classmate of Kyoko's, who becomes her future partner. ==Volumes==