From the introduction: Before currently recorded history, there was a golden age, ironically called the Silver Millennium. Humanity developed advanced technology and colonized other planets in the solar system. A kingdom was developed, and with all kingdoms, the need to protect them. Using the the Star Seeds of the planets, the royalty became Sailor Senshi and fought to protect their planet kingdoms. Star Seeds were the crystals that embodied the life, and perhaps existence, of the person carrying it. But while normal humans had their weak, near powerless star seeds, the senshi carried the Star Seeds of the celestial body they ruled. These star seeds were called Sailor Crystals.