The Demon God Who Should Have Been My Archenemy Became My Sibling

In the Kunlun Realm, General Xuanyuan commanded a million celestial soldiers. His sworn enemy was the demoness Chi You, who came from the demon realm. Ever since the war between immortals and demons began, they had fought 9,999 times. In their final battle, both fell into the mortal world. As they lay dying, they independently chose to reincarnate their souls into the bodies of the nearest mortals. By coincidence, those two mortals turned out to be siblings. Thus Xuanyuan became the older brother, Xia Changkong, while Chi You became the younger sister, Xia Yufei. Both retained their former memories. Though they should have been enemies, they had no choice but to live together as siblings. What will happen?