Reunion: The Murderous Equation (1988)

One day, Mio, a reporter, is shown a manuscript for a contest by Kuribayashi, the editor-in-chief. The manuscript, which she is told will likely make it to the final round, is that of Kashiwagi, who was supposed to marry Kuribayashi's daughter. Hearing the familiar name, Mio learns that Kashiwagi is now married to the daughter of a top company and holds a high position. The two are nostalgic about their reunion, but soon after, a series of murders occur. Mio investigates the case to prove Kashiwagi's innocence, even though he was suspected of murder.