My best understanding of the case if that the girls are tricked into signing a contract thinking they are going to do regular sex scenes, or even rough scenes perhaps, but then get r***ing for real. Like the other user said, lots of jail time was handed out. The video definitely is out there so it was either taken down with remnants remaining on the internet or the video is kept out there because it sits in a legal grey area.
Here is the Japanese wiki page for Bakky:
https://ja.wikipedia.org/wiki/バッキー事件
This is a translation (I used ChatGPT rather than Google Translate):
"Bakky incident" is a case of r*** and injury committed by the video production company "Bakky Visual Planning" against AV actresses and amateur models.
Chronology:
In late June 2004, Bakky Visual Planning (referred to as Bakky below) lured AV actresses to an apartment in Nishi-Ikebukuro, Toshima Ward, Tokyo after making them inhale drugs (illegal drugs) at an izakaya in Toshima Ward, Tokyo, and while filming obscene acts, they inserted an enema device into the anus and ruptured the device, causing serious injuries such as rectal perforation and anal lacerations that required 4 months of medical treatment for recovery. The crime was heinous, and if treatment had been delayed, there was a possibility of death. The police were called to action. The victim suffered long-term effects such as having to have an artificial anus attached[1] (the mortality rate after rectal perforation surgery is said to be 40%). On December 16th, 8 people, including Ryo Kuriyama (real name Ryo Kuriyama), the representative and H manager, were arrested on suspicion of forced obscenity.
Bakky had previously produced a large number of violent videos, including kidnapping, pubic hair burning, water torture, and forced drinking, and had also established a group called "Kankin Tomodachi no Kai" (Association of Kidnapping Friends) and recruited extras for filming from DVD buyers. None of the details of the filming were known to the actresses, and the filming of these violent videos was carried out without their consent[2].
The arrested individuals were released with the disposition pending due to insufficient evidence, but after this incident, the Ikebukuro Police Station began to take decisive action to destroy Bakky. Actresses who appeared in Bakky's videos submitted complaints to the police one after another, and in March 2005, the individuals involved were arrested again. Kuriyama, who was accused of blaming the filming staff, was arrested and indicted for r*** and injury in February 2006.
Kuriyama, who is considered the main perpetrator, and the male director were indicted in the Tokyo District Court, and Kuriyama's closing argument and sentencing trial were held on October 5, 2007. During the hearing, it was revealed that multiple acts of violence beyond the scope of filming, such as assaulting a woman who was deceived into thinking she was participating in a mild r*** scene by administering illegal drugs and sleeping pills, and repeatedly committing violence for more than 10 hours by tying her hands and feet and submerging her face in water, were carried out by 20-30 people. The prosecution sought a 20-year prison sentence, stating that there was no room for leniency due to the lack of remorse and the severity of the violence. However, even during this time, the defendant reportedly smiled faintly [3].
On December 19, 2007, the Tokyo District Court handed down a sentence of 18 years in prison to Kuritani, and the Tokyo High Court also issued a similar verdict [4].
