Chapter Text
The Solar system is a star system somewhere in the vast cosmos.
The Sun is the local star of the system, and the system has eight planets, namely Mercury, Mars, Earth, Venus, Jupiter, Saturn, Uranus and Neptune. The first four planets are rocky planets, while Jupiter and Saturn are gas giants. Uranus and Neptune, situated far away from the Sun, are ice giants.
A belt of asteroids enclose the orbits of the rocky planets, and beyond the orbit of Neptune, there is a significant dwarf planet, named Pluto. Further beyond is the Kuiper belt, which marks the frontier of the Solar system.
Each planet has its own guardian, even those outside the habitable zone. For millennia, they have lived in solitude, watching over their respective planets for the entirety of their lives. These guardians are vastly different in many aspects, but there is one thing in common among these guardians.
All of these guardians have magical powers, and their uniforms are reminiscent of a sailor's uniform. They are hence known as the Sailor Senshi.
Earth is the only planet in the habitable zone of the Solar system. Its moon, the Moon, is home to a woman who is tremendously strong with the cosmic Force. Her name is Selene.
Selene built a kingdom on her moon, and as years passed, technology progressed under her reign. Her people, the Lunarians, have developed vessels capable of transporting passengers and cargo around the Solar system.
A few years after the first Lunarian space vessel was built, Selene ventured around the Solar system. The Sailor Senshi, having lived their lifes in a seemingly perpetual solitude on unhabitable planets, were astonished to see Selene arrive on their planets.
"I am Selene. I am offering you a chance to break free from perpetual solitude. Join my kingdom, and you will receive the title of 'Princess', and your planet shall be protected by a stronger force forged through solidarity. Unity makes strength, so please accept my offer."
After travelling to all the seven lifeless planets and recruiting their Sailor Senshi, Selene effectively rules over almost all of the Solar system. The original generation of the Sailor Senshi retained the uniforms they wore before joining the Moon Kingdom, but after they passed away, their subsequent reincarnations wore a standardized uniform to signify their unity and common allegiance to the Moon Kingdom. The Sailor Senshi of the rocky planets and Sailor Jupiter were tasked with protecting peace within the Moon Kingdom, while Sailor Saturn, Sailor Uranus, Sailor Neptune were tasked with protecting the Moon Kingdom from external threats.
Earth was a habitable planet, and hence, the Sailor Senshi of Earth, unlike all others, did not live in eternal solitude. Because of this, Selene had no plans to recruit the one who guards over the Earth.