How could my childhood sweetheart be the current empress?

Xu Chengling traveled through time and space to become a villain in the book. The current empress is about to regain power and rule the world. In order to avoid being exterminated by the empress, he had to get along well with the empress's well-behaved and shy sister since childhood, so that she could marry him in the future and fight against her together! But his plan went a little wrong.
After marriage, the lovely and well-behaved Qingmei Lady became aloof and steady, managing the mansion in an orderly manner, while the empress who was supposed to be cold and majestic became...