Oh My Savage Princess!
Completed with 178 chapters FL is a queen of the netherworld and the ML is the emperor of limbo which i guess is a pretty big deal so apparently he and her brother had a fued which resulted in her getting abused by the other realms so one day she transmigrated into the body of a princess and the ML is the regent she didnt know that he was the dude that she fell for when she was a kid and was actively pursuing him So she lived in this body and kicking asses while also dealing with all the supernatural shit going around and finding out how to find that crush of hers and her brother turns out why the brother did what he did was to seal this separate dark being within her and well in the end she defeated that side of hers and she got married to the king of limbo she found out about his actual identity but it wasnt such a big deal cos she fell for both of them and turns out to be the same person little to no drama
I Worked Myself to Death and Reincarnated as the Queen of His Majesty, Who is Younger than Me!