the other princess(ig she was blonde) regarded as useless was sent off to marry the prince(black hair( of the neighboring country they both aren't interested in each other and something like princess of the duchy of the kingdom was aiming for the throne and she uses dark magic and she accused princess of smth and she was under house arrest oh yea the princess had a wizard friend who years back defeated the demon. The demons are back again because the duchy princess summoned them. That's all I remeber :<.
It looks like this : https://www.mangago.me/read-manga/the_black_haired_princess/
Measa ming mechik sakgnian kisangbak sa