Trying to Remember the Name of An anime

xin chào guys. So a while cách đây (I can't even remember exactly how long cách đây but I know it was in the span of the last 6 months hoặc so) I watched this clip about an anime.
On of the main characters was a boy and he was some sort of knight, I think. I think his hair was green, but don't take my word for it. The other main character is female and she was some sort of magician and I think her hair was blonde.

In the series, the girl swears to the the protector(?) of this knight-boy-person. She also harbors feelings for him.

I do not think the anime is a harem and I'm not sure if it counts as Isekai but it was definitely in some sort of historical fantaisie world. I think the anime also talks about politics...?

If this sounds even distinctly like an anime bạn know, please let me know!

Thank bạn so much!