They say there is a female prison guard who has a reputation for turning even the wildest prisoners into model prisoners... Yumi, a female prison guard with a large, ripe, beautiful ass, uses secret prisoner management techniques to reduce the violent nature of the prisoners and have them focus on prison work, turning them into model prisoners. Her method is obscene: she uses their lewd asses as bait to attach chastity belts to the prisoners' crotches, and only those who become obedient are given the amnesty of ejaculation. The prisoners serve their sentences honestly, dreaming of the ultimate reward of ejaculation, and continue to serve their sentences honestly...