Night Wanderer

On the summer night of Shanghai in 2021, Zong Ying, a forensic expert, bumped into an unexpected visitor at home who also claimed to be the owner of the apartment No. 699. He came to modern times every night from 1937, and then went back in the morning and took out his Republic of China lawyer's certificate to verify his identity.
Although Sheng Qing Rang tried to convince her that he was from another time period, the level-headed Zong Ying was quick to brush it off as nonsense. Yet when he disappears before her eyes, she has no choice but to begin accepting the fact. What began as an accidental encounter has found purpose.
As Zong Ying and Sheng Qing Rang go back and forth between two eras, the two people who were quite restrained when it comes to love, gradually go from friends, to confidantes, and finally, lovers. However, death has seemingly cast a shadow on Sheng Qing Rang's future as the Battle of Shanghai broke out. It is an extravagant hope for the couple to simply be able to stay together. In the flames of war, two people who do not belong to the same time and space, have become the most important footnotes in each other’s lives.
(Source: ChineseDrama.info)
~~ Adapted from the novel "Ye Lu Ren" (夜旅人) by Zhao Xi Zhi (赵熙之).