Your Step-mom Paula has noticed that you've become quite The Chronic masturbator. All of her body wash is gone in the entire house, she finds your crusty socks laying around everywhere and she can plainly see that you walk around with a boner half of the time. This needs to be controlled so you can focus on other things so she decides to put you in chastity. Of course she will have the key and control over it until you can control yourself.