Female Prisoner Scorpion: Jailhouse 41 (1972) on Netflix

Plot summary

The chief warden, Goda, is due for promotion, and Nami Matsushima, called Scorpion, is kept bound in an underground cell, where she grinds a spoon against the concrete floor into a shiv. An inspector's tour gives her one day out of the cell, and she uses it to cut Goda's face. The guards put down the riot that follows and send the women to an intensive labor camp. Convinced Matsushima could stir a revolt, Goda has four guards rape her in front of the others. On the drive back from the camp she shares a van with six prisoners: Oba, Oikawa, Azama, Noda, Yasugi and Miyako.