Not everyone gets to be the heroine of her own story, much less a champion for others. On May 29, 2017, a 28-year-old Japanese journalist, Shiori Ito, did just that when she announced at a news conference that she had been raped in a Tokyo hotel two years earlier by a powerfully connected journalist, Noriyuki Yamaguchi. (He has denied the allegation.) Ito had decided to speak her truth despite intense pressure to remain silent. “People need to know about the horrors of rape,” she told a room of reporters, “and how deeply it affects one’s life.”

Undaunted, Ito talks openly throughout “Black Box Diaries,” her moving if sometimes frustrating documentary about how she became a public face of the #MeToo movement in Japan, all while she grappled with police obstructionism, misogynist laws, sexist vitriol and fears about her safety. Going public was gutsy, and unusual. “One of the first things many Japanese women do while still shivering and bleeding at home is to read online about the experience of others — and deciding it’s just not worth pursuing,” David McNeill, an editor at Asia Pacific Journal, wrote in an interview he did with Ito after her first news conference.

At the time, to protect her privacy, Ito wasn’t using her surname; not everyone in her family wanted her to speak out. Yet she soon went fully public, and her name became headline news. It remained so as she continued to seek justice in a fight that — as one year turned into another — grew into a cause, eventually becoming part of a national reckoning on sexual violence and harassment. With friends and lawyers, and buoyed by allies and sympathetic strangers, Ito fought to transform Japan’s laws and ideas relating to sexual violence. (In 2023, Japan criminalized nonconsensual sexual acts; in 2019, the United Nations had issued a statement saying the “absence of consent” should be the global definition of rape.)

The documentary, based on her 2017 memoir, “Black Box,” is a chronicle of Ito’s ordeal and her fight. As the title suggests — a prosecutor, Ito has explained, called her case a “black box” because it happened behind closed doors — there’s a confessional aspect to her project. The documentary, for one, opens with some first-person statements styled as handwriting, the words running over an image of flowing water. “Please be mindful of the triggers in this film,” it reads, as cherry blossoms drift across the screen. “Close your eyes and take a deep breath if you need to.” As water and petals flow, so do her words: “That has helped me many times.”

What follows is effectively a tense and tangled crime story, one in which Ito is at once the victim, lead investigator, dogged prosecutor and crusading reporter. In 2015, following the assault and after she filed a criminal complaint with the police department, Ito realized that she had to become her own advocate. She began chronicling the investigation in secret audio recordings, detailed written records and videos. After prosecutors dropped the case, despite DNA evidence and testimony from a taxi driver who dropped her at the hotel — she decided to take her personal investigation to the world.

A sense of personal urgency informs Ito’s overarching approach in the documentary, which restlessly, somewhat jaggedly, toggles between her struggles in private and in public. To shape her story, she draws from archival and original material, including home movies, surveillance imagery, news reports and even a recorded chase sequence. The most striking and emblematic materials, for better and not, are the diaristic cellphone videos shot by Ito and assorted collaborators. In some videos, Ito speaks and at times weeps into the camera as if she were FaceTiming a friend, while in other clips, she sleeps, eats and goes about life.

The movie’s intimacy is appealing; on occasion, it can be claustrophobic. “Black Box Diaries” is, at heart, a first-person account, and while it’s successful on those terms, it’s finally more emotionally engaging than intellectually satisfying. Throughout, Ito puts her story into greater context by, say, folding in information about Japan’s rape laws. In July 2017 — just weeks after her initial news conference — the Japanese parliament passed the first changes to the country’s sex crime laws in more than a century. Yet while Ito speaks to other women, some of whom share their own painful truths, what’s missing is a better sense of the larger collective effort that these voices represent in the continuing movement toward equality.