On the planet of Hekiou, there is a continuing war between the first wave of immigrants and the second. An important section of the military uses a native creature, the Niebass, to give its soldiers translocation abilities. These soldiers are all women, with the alien creature transplanted into their wombs. Some people see this practice as a violation of human women by aliens, and Mana Oga's boyfriend has a similar perspective on the matter. Mana Oga is a new soldier in this section, and the story follows her and the other women in her group who accept the alien creatures into their wombs in order to defend their homes.

(Source: MangaHelpers)