Our world was peaceful. Only that it was no longer our world. The Souls, an alien kind had taken over the planet just as the other planets they had colonized. Very few humans still existed and they were on the run in order to hide from the Souls.

Sehun was supposed to be one of his own kind. The alien kind. The kind, honest, generous kind. It had been almost seven years since the first wave of colonization by the Souls. They had taken over Earth and had taken control of every body on Earth. N31D was brought over from his planet, the Origin and was inserted into the body of Sehun. Now, he lived as Sehun. Only that the life was no longer Sehun's. Some Souls experienced the protests by the original owner of the body. But Sehun was already brain-dead before N31D was inserted into his body. Sehun's body was repaired and a Soul was given full access to the body.

Earth was his first planet. And a human body was his first body. When the mind was regenerated again, the memories started to haunt him. The memories of Kris. Unable to control the way the body reacted to the memories of the body's previous lover, he set forth to look for him. Never did he imagine how much Kris actually hated the Souls. Worse than him, it was Kai, Kris' brother who loathed the aliens to hell's pit.

He embarked on a journey to find Kris, leaving his perfect life and community behind, going against all the rules. What he didn't plan was to fall in love with someone else. The body loved Kris. But the Soul loved Kai. 

http://www.asianfanfics.com/story/view/755631/sui-generis-mpreg-exo-kai-sehun-kray-sekai-thehostau