Yoake Mae yori Ruri Iro na centers around Princess Feena Fam Earthlight from the Kingdom of Sphere on Earth's moon. It was decided that she was to live on Earth in a homestay with the family of the primary secretary to the president of the United Nations so as to get more knowledgeable of Earth in order to better prepare herself for her succession as the Kingdom of Sphere's next queen.

The background of the story explains that humans landed on the moon long ago intending to create a new home for themselves called the Kingdom of Sphere. However, the relations between Earth and the Kingdom have worsened and things a war called the Oedipus war started. Once the war was over, it was decided that the city of Mitsurugasaki, where the story takes place, under the rule of the United Nations, be developed as the center of diplomacy with the Lunar Kingdom, which, currently, has closed its doors to the world. This central lunar junction port city, which has the only spaceport within the United Nations with ships going to and coming from the Lunar Embassy, is, as its name suggests, the gateway which connects the Earth and the moon. Although tensions have temporarily eased now, relations between the two worlds is still in a situation when the story begins where caution must still be taken.