Crest of the Stars

2012 manga running in Comic Meteor.

Crest of the Stars follow Jinto Lynn, a young count whose world is taken over by the space-dwelling race of the Abh. When Jinto was a young boy, his father, Rock Lynn, under threat of invasion, handed over their world, Martine, to the Abh in exchange for a position within Abh society. Young Jinto is sent off to school to learn the ways of Abh nobility and the story of Crest of the Stars picks up as he meets the young Abh princess, Lafiel as they are about to travel to military school for Jinto's further training.

However, in the midst of their travels, Lafiel and Jinto (along with the Abh ship Gothlauth, a.k.a. Gosroth) find themselves at the very beginnings of a war between the Abh Empire and the Four Nations Alliance of humankind—an anti-Abh alliance of the democratic nations of the United Mankind, the Federation of Hania, the Republic of Greater Alcont, and the People's Sovereign Union of Planets.