Based on

Movies like Subway Serial Rape (1985)

A man with a briefcase is being pursued by a small yakuza gang. After abandoning his vehicle, the man boards a train where he and the other passengers watch a woman being assaulted by three thugs. Intimidated, the commuters do nothing to help. Later, the victim reports the incident to the police and a witness finally comes forward. When the man hears about rape on the news he takes steps to protect his identity and begins to track the victim.