Copy of Tokyo Metropolitan Police File:

On Friday, April 1, the lifeless body of a man of about 25 years of age appears in the services of the Ueno station (Tokyo).
Cause of death: Homicide with a knife.
Approximate time of death: between 9 and 10 p.m.

The suspects are four men and two women who are traveling on the Yuzuru #7 night railway (the blue train), bound for Aomori.

Seven years after graduation, a group of friends decide to take a weekend trip to their hometown. What seemed like a happy reunion will be cut short when one of them is found murdered minutes before the train leaves the station. The police suspect that he may not be the last...

Thus begins an investigation against the clock to catch the murderer before he commits more crimes.