Koike Aya

Koike Aya is a 9 year old girl who Ida crosses paths with on a case in volume 7 of Jiraishin. She appears to be a sociopath, and very mature for her age. She also shows no remorse for those who have died, not even her friends. As a result of her mischief, Ida is caught in the middle of what she believes to be a game between two forces called 'Thrill' and 'Real'. This results in Ida having to go up against a killer that she drove over the edge, who now intends to kill her. In the end, Ida tricks the killer by making him think that he'll let him escape with Aya. She panics, thinking that Ida has left her to die. Ida ambushes the killer and takes him out with a single shot. Thinking that the blood-covered Aya has learned her lesson, they part ways. She returns again in volume 15, after 3 years, seemingly showing no remorse for the fact that 4 people were killed because of her in the past, to assist Ida on a case.