It’s Just Fortune-Telling. How Did the Nine-Tailed Demon Emperor Become My Wife?

Jiang Jue enters a world of xianxia and gains a Destiny Deduction System that lets him read people’s fates, learn about their pasts and futures, and even alter their destinies. The system comes with one troublesome rule: whatever he predicts, he must tell the person exactly as he sees it. When Tu Shanlan, ruler of the Ten Thousand Demon Kingdom, asks him for a reading, Jiang Jue predicts that she will marry and have five children thousands of years later. He then adds that he will be her husband.