Ever since the fall of the late President, Seoul has seen its downfall as the mysterious mafia group named 'Alpha Numera' made its appearance, causing crime rates to skyrocket exponentially. Desperate to salvage the city, the remaining government officials has ordered PROJECT: Hydra to be forced - where teenagers are forcibly contracted with Devils to grant them immense power.

Jung Jaeri, along with her twin brother Jung Jaehyun have never seen the sun, having spent their entire lives in the facility. But when they are suddenly pushed into the outside world they have never seen before, it doesn't take them long to realise that the concept of freedom is merely an illusion.