For as long as she could remember, Choi Hyejin had been at YPM: if anything, a sort of secret police in Korea.

It's where her home is, where her job is, and where her little brother and friends are. It's all she's ever known. From the time she could speak she was reciting the YPM code, and as soon as she started to walk she was learning to fight. 

For nearly all of her 21 years, Choi Hyejin's has been at this, doing this: completeing missions, no questions asked...

but then came the one mission that undid it all.