The number of humans has plummeted in a world where a deadly poison was spread by the explosion of a research facility. One day, Professor Murase discovers a girl who was preserved by a capsule. In a world where there are no young women, her existence has become the saving grace of humanity.

Following years of war, men have become scarce, and gender distinction has almost vanished in society. Reproduction is mostly achieved through artificial insemination.

Ensign Koizuka has been called back from the front lines to serve as Personal Guard to the Princess - whom she loves - during her upcoming wedding celebrations. The princess is getting married to the eccentric queen of a large country, in the hope of appeasing the more powerful monarch's geopolitical ambitions.

It soon becomes clear that the queens' designs may not be in the princess' best interests. Koizuka, who was the one who revealed the princess' feminine side and got her noticed by the queen in the first place, is torn between jealousy and a feeling of responsibility.

In the midst of all this, Koizuka's Captain confesses her love...