The recommended novel, Pet Killing Agent Girl: Killer Queen, Dragon and Phoenix Baby. The protagonist of the novel was a female agent who had traveled back in time to ancient times. She was skilled and later traveled back in time to become a useless young master of a family with a bad reputation. She disguised herself as a man and became a daring person. On the way, she met a cold and handsome black-bellied man. The Emperor seemed to have fallen in love with her. The protagonist also gave birth to a pair of baby dragons and phoenixes. It was a novel about time travel, and the plot was similar to the description of the title. I hope you like my recommendation.