Dance by the River

"Ukishio stabbing: 14-years-old girl arrested."
In Ukishio City, a suburb of Saitama Prefecture, a stabbing incident occurred that left 1 killed and 3 injured.
Even though, at first, the local newspapers only reported it, the suspect girl was arrested, the next day, the national newspapers made headlines.
As is often the case with violent or ugly news, for a short period, this news also created a sensation and people said whatever they felt like.
After the trial, her diminished responsibility was demonstrated, but at that time, nobody, except few concerned, was interested anymore.

Three years later, a police officer, Issei Tegoshi, was transferred to the Ukishio Police Station in his hometown.
He was assigned to the Juvenile Case Investigation Team at the Community Safety Division. In this division, he works under a non-career-track female police officer, Ino Sarina, who graduated from the Faculty of Law at the University of Tokyo.
As Tegoshi begins to have a difficult time with too straight-laced Ino, an incident occurs.
It strangely looks like the three-year-earlier incident in Ukishio City...