You wear it

You lift up the cock cage apprehensively, and your phone chirps.

"Put it on if you wish to save Ms. Yun-Seung. Or leave if you don't."

You hesitate, and the belt begins stimulating Kim behind you, making her thrash and swear loudly. "F-fuuck, fuckkk! Fuuuucking fuck!!!" She sounds so **** that her curses are more like sobs, and the heart-rending quality to it finally makes you give in.

Dropping your pants, you put on the cock cage reluctantly, fastening it in place with a feeling of dread. With your cock locked inside, you don't see any way of getting it out safely unless someone provides you with the key...

You hear the buzzing of Kim's chastity belt cease, then hear a click, followed by a startled noise from Kim.

As you turn to face her, she tosses her dislodged chastity belt to the ground and rushes you, hugging you tightly without seeming to care about the state of undress either of you are in.

"Thank yoouu, thank you, thank you, thank you!" Kim buries her face in your chest while thanking you repeatedly. You're feeling pretty good about your altruistic deed for a few moments, but then your phone chirps with one message after another from 'them'.

"Congratulations on freeing Ms. Yun-Seung. You are now however our property in her place."

"As your chastity device is not equipped with any way of sexually stimulating you, your first task is to convince someone to perform this for you. If you're unable to do so, you'll be unable to earn your freedom any time in the foreseeable future."

There's a pause, then another message. "We recommend you request Ms. Yun-Seung's help in this matter. She is after all greatly in your debt."