Can you recommend a romance novel?

The story was about the female protagonist marrying a CEO in the modern era and traveling to the ancient era. She was disguised as a man and fell in love with the man who protected her. The female protagonist returned to the ancient era at night in the modern era. When she slept in the ancient era, she returned to the modern era. The CEO in the modern era finally died and she gave birth to a son for him. In the end, she married the man in the ancient era and gave birth to a son and a daughter. Who knew the name of this book? It may not be written in detail

Answer 1

[Guide to the God of Learning]