FL and ML was in military together, but ML became the emperor and he asked FL to help him as his concubine and later he push her to be his empress since he loves her and don't want to see her bowing to other concubines.

I read this manga years ago on otakumole and already forced my brain to remember the title, but i still can't remember, please help me finding this one.. if i'm not mistaken, there are some chapters in english already by borrowing otakumole's translation..

https://www.mangaupdates.com/series.html?id=133426

I actually came on this forum trying to find this series and remembered the title bc of your description