10,000 years ago, there was a war between Heaven and Hell being fought on our earth. Both sides were launching their strongest forces, but it always ended in a stalemate. Enter Xiao, angel of heaven sent to nullify the war and find the most powerful demon and kill it, but when she finds it, it turns out to be her best friend. As punishment, God imprisons her and the demon into special cases. 10,000 years later, the descendant of that very same demon that was imprisoned along with Xiao frees Xiao and the demon accidentally. The events that unfolded later are documented in this story, D Station Squared.