Zhuang Po Huangdi Nüer Shen

After transmigrating to another world as a wealthy young master, Su Changqing only wanted to live a low-profile life as a rich second-generation heir and enjoy his days in comfort. However, his plans are suddenly disrupted when his family faces an unexpected crisis, and he accidentally discovers the Emperor's secret - that she is actually a woman. While he initially feared the female Emperor would stop at nothing to silence him, to his surprise, she instead becomes interested in his mysterious ability to transform his appearance. She wants him to become her male body double. What Su Changqing never expected was that being the female Emperor's male substitute would mean he has to visit the imperial harem on his very first day. His peaceful life completely falls apart from that moment on... (Source: Bilibili, translated)