If you had to choose an identity to go undercover, you'd choose a gynecologist.

Espionage + Multiple female leads + Lighthearted slice-of-life + Dark and scheming + Fanfiction of a spy drama.
This book is a spy-themed fanfiction with multiple female protagonists, including Wang Manchun, Yu Manli, Mingjing, the landlady, etc. Chen Qing, a rich second-generation who is good for nothing, is reborn in Shanghai in 1939 and becomes a low-level liaison officer in the Kuomintang liaison station.
The male protagonist awakens a gynecological expert system, which allows him to see the ailments inside women's bodies. He opens a gynecological clinic to disguise his identity. However, women in this era are very conservative, and business is slow. Until one night, Wang Shen, a Red Party agent being hunted by the 76th Division, breaks into the clinic and stuffs a box of glue containing Japanese military secrets into his mouth...