I read the manga only a few months ago, but I can no longer find it. It had a decent amount of chapters already translated to English. While I'm not completely sure, I think the amount was somewhere in the 30s.
The story is about a princess. If I recall correctly, she has two older brothers who were fighting over the right to succeed the throne. To avoid all of that, her father (the king) decided to just make that princess the one to become queen.
Because of that stuff, I recall her having some nickname along the lines of 'leftover princess'.
I think I recall the name of the princess starting with an 'L'. I also remember her using Cia, or Sia (something like that) as an alias when going into town.
I'm not sure for the reasons behind it anymore, but that princess had to form this order of knights to serve her before she could become queen. Where the story was when I read it, she had 2 people in that knight order. I think one of them was called Duke, or something along those lines.
I think she also had the ability to go to some place where there were past kings of her country and she could talk to them.
There was also a part I remember where she mentioned having the powers of some swords in her. Like 12 or 13 swords if I remember correctly. She used the power of one of them to save someone from a curse at one point.
With the amount of similar manga I've read, I'm not 100% sure about much more, but I'll be glad to answer any questions that might clarify things if I'm able to.