After they capture Academy substitute teacher Rika Shiraki, Reika Kitami's followers Kaori Saeki and Saki Kiriya use the device to brutally torture her as punishment for supposedly spying on them. They tie weights to her feet and nipples, and insert a vibrator inside her, inflicting horrible suffering on the woman's body.
They later threaten to do the same to their former ally Yuki Toudou when the young student reveals herself to be a spy for the elusive Jody Crowley. A fitting punishment for betrayal, considering the device's reference to JudasWP.
Shiraki is eventually released from the device, and proceeds to urinate on the floor.
- Judas cradle on Wikipedia.