The promising detective Kiryu Aoi realizes her long-cherished wish and takes a job at the police station in Yonomachi, a suburb of Tokyo.Aoi's partner, Kei Kasaka, a detective at the Nozomi Department, was puzzled as to why she came to the Nozomi Department and began to investigate.

Yono Town is Aoi's hometown and the place where two murders occurred 16 years ago.The victims in that case were all young women, and their bodies had their mouths filled with marbles.Aoi, who was still a high school student at the time, discovered the body of the younger sister of her favorite classmate Sho Fuwa.Aoi was so shocked that she lost her memory before she found the body.

Soon, Aoi's father was arrested as a serial murderer and died of illness in the detention center.Aoi, who became the daughter of a vicious criminal, left the city.

Sixteen years later, Aoi, who believed her father was innocent, returned to Mochino Town in order to explore the truth of the incident.

Aoi reunites with Megumi Oto, Yuki Amakusa, and Momo Asuka, who are also classmates in the Image Research Department.Another partner, Fu Po, disappeared after the incident 16 years ago.

At this moment, the Wangye Police Station received news that the female high school student was missing.Kento Ichijo led the members of the Hope Field Office to go together.Then Aoi and Kasaka discovered a marble similar to that incident.On the other hand, Kosaka's former boss Takeshi Arimura issued an order to Kosaka to monitor Aoi.

Around WangyeTownTaking the new incident as an opportunity, Aoi continues to search for the real culprit of the serial murders, and, toOver the past 16 years, thisTownThe hidden truth challenges——!