This is the remarkable story of Japanese journalist Shiori Itō, who waived a legal right to anonymity to pursue her rape case against prominent TV news executive Noriyuki Yamaguchi. The film gives us fly-on-the-wall video footage of her embattled life as she prepared her legal case and later as she wrote her memoir of the events, Black Box, named after the closed files on her case: the black boxes.

As a young journalism intern in 2015, she had turned up for what she thought would be a career-help chat with Yamaguchi. She was confused and uncomfortable to find it was at a bar where turning down his hospitality would be impolite; she became drunk and says she regained consciousness in a hotel room to find Yamaguchi raping her. Later, in a police station, officers made her re-enact the event with a male dummy. Itō became the figurehead of the Japanese #MeToo movement as hundreds of thousands of women in conservative, male-dominated Japan examined their own supposed memories of abuse. And as a journalist, Itō found herself on the trail of a Watergate-type story: her assailant was friendly with the Japanese prime minister and with police authorities who cancelled his arrest warrant. And all the time, she received a blizzard of online abuse. Yamaguchi maintains sex was consensual.

Perhaps without her previous educational experience in the US, Itō would not have been inclined to pursue her case. The film makes it clear that Itō had allies: an investigating officer in the Tokyo police gave her secret information on condition of anonymity and, more sensationally still, a hotel employee went on the record to testify he saw Yamaguchi carry a clearly incapable Itō into the building.

It is from the hotel that Itō got her most chilling evidence – the CCTV footage of Yamaguchi bundling her out of the taxi outside the building – but my only mild criticism of the film is that it could have given us an exact account of how they got this devastating piece of video. Itō is an amazing personality: an intelligent, courageous journalist who may have changed the course of Japanese history.

• Black Box Diaries is in UK cinemas from 25 October.