Synopsis for Kensaku Watanabe's Prison 13 - a.k.a. Purizun 13 and Purizun sâtîn - from the movie's international sales agent, AMG Entertainment Inc. (AMG Entateinmento K.K.): "A high-price reward of 1 million yen for a 7-day experiment... Mari (Mayu Hotta), who was chosen as a test subject for an open experiment of a popular VTuber, Sophia, finds herself in a strange laboratory in which a giant 4-meter square cage is set. The 12 test subjects are given roles as prisoner or warden according to Sophia's directions, and the experiment begins. Mari, who was chosen to be a warden, allows the prisoners to run wild due to her kindness. The outraged wardens bully the prisoners for fun, and Mari's position is endangered as well. As the experiment heats up, the experimenter Sophia stirs up the situation even more, and the existence of a 13th test subject is hinted at. The broadcasted videos are uploaded twice each day, and record an overwhelming number of views. Mari's older sister Yuma (Tomomi Itano), who follows the broadcasts, takes action to save Mari with the help of her husband, Kouki (Tomoya Maeno), but..."
