They were born different, their anatomy changed by the powers of the Five Angels. They were taken from the Five Angels by a Shadows spy and brought to Earth.

Their lives spiralling out of control as they are hunted by the Shadows. They stand out like a sore thumb, bearing large wings with a wingspan of fifteen feet and special powers. They are on the run, trying to reach the safe haven of Planet K, they were promised by the Angels. The Shadows had burned off all the routes to planet K years ago. All connections with the Five Angels were cut off as well.They have no idea where the Planet K is, or when they will find it, but they know when they find it they are finally safe from the never ending chases by the Shadows.

The Angels who had created them had named all twelve of them, a flock, EXO, and they were used to build the structure of Earth and several other planets including planet K. But the Shadows, the anti-Angel society, want to use them for the destruction of Earth, and use the power of EXO to create their own planet.

They are never safe and never will be until they find The Lost Angel. The Lost Angel has the power to mend all the routes to Planet K and get EXO back to the Angels, but the thing is, The Lost Angel is a myth. The leader of EXO, Su Ho had been searching his whole bird life for The Lost Angel and has never found any signs of it. Nobody knows if The Lost Angel is real, but the hope for future burns bright as the never-ending quest bears on.