You !

"Silass! To the board, your countdown starts now. 30, 29, ..."

Taken by surprise you quickly get on your feet and rush to the board.

"25, 24, ..."

You look at the equation but nothing comes to your mind.

"10, 9, ..."

Shit shit, what is this equation ! It's impossible to do in such a short time!

"3, 2, 1, 0. ... So Silass, you don't have the answer ?"

"No miss."

"Pathetic, we clearly did that last week." she says erasing the blackboard without giving the answer. "I can't accept to have students slacking off in my class so, to make sure that you study and your results improve, I will have to keep your key for a month. On the first day of next month, you will come back to the board to solve another exercice and try to win your key back. Now go back to your seat." she tells you as she slaps your butt with her ruler.

The rest of your day is uneventful compared to that.

At the end of the day, when passing in front of the secretariat, you see Ms Ren collecting your key there and putting it on a collar around her neck.

It's your first time not being able to remove your chastity cage once back to your appartment.

As the day pass, the constant arousal caused by all the indecent posters put up around campus, as well as the revealing outfits of the futas, and Ms Ren proudly wearing your key around her neck, clearly in view since she decided to start wearing more open cleavages, all starts to wear on you. Your cock is always prevented from going hard and you are not able to get any releaf. By Friday you even started to make wet dreams about the posters you see around campus. During the weekend, you try to focus on studying Ms Ren classes to be able to recover your key but it's quite hard because everytime you think of her classes, you also think of your key, your locked cock, and her cleavage, and ... also her tight suit with it's bulge. What is happening to you ?

Meanwhile, a new rule has been implemented. Following a complaint from the school staff about unruly students, all school staff are now authorized to give out punishments and in particular to take away keys.

The month goes by and the first day of the next month finally arrives. You tried your best to study but it was hard focusing and you slept very little, getting woken up in the middle of the night by your dick trying to get erect from your wet dreams.

You arrive in Ms Ren class and at the end of the class, she calls you to the blackboard to answer a new problem.