 If you liked Zettai Heiwa Daisakusen |  ...then you might like Akatsuki no Yona |
It is set against a background of political war and intrigue, and has royalty and nobles as the main characters. In both we have a lot of political unrest and assassination attempts going on and both have a strong story and plot. In Zettai we have romance and I am hoping this to be the case for Akatsuki no Yona as well. Both have young women who are set against trying circumstances and both girls are not in love with the male characters to begin with and the guys have to try to win their hearts or they realize
When it comes to royalty, both series' main characters are no strangers to such a title. While their premises aren't alike, their storytelling has a similar trend with the female character getting involved in political affairs that turns sour. Both series' female protagonist also has similar personalities and they also develop important relationships with others, in particular the main male protagonist. There is also evident romance as the story progresses as well.