In Sailor Moon, each planet in the solar system has a warrior assigned to it. Only the Earth itself does not have a Sailor Earth, who takes care of the planet. However, there is actually a person in the anime who protects the Earth as a guardian, and it is not Sailor Moon.
Who is Sailor Earth? There is no direct Sailor warrior for Earth that protects the planet. Instead, Mamoru Chiba, Sailor Moon’s friend, takes care of the Earth’s safety. In his heroic form as Tuxedo Mask, he faces the villains, even if he sometimes fails more than succeeds.
Even though the other Sailor warriors protect the Earth, they are actually assigned to other planets. Sailor Moon herself actually comes from the Moon and has nothing to do with Sailor Earth. The missing link that completes the Sailor warriors is Mamoru. And there is a reason why there isn’t a true warrior.
The name of the remake Sailor Moon Crystal already reveals what it’s about:
Crystals determine who becomes a Sailor warrior
Why is there no own warrior? In the manga, there is an explanation as to why Mamoru is the protector of the Earth but cannot be a true Sailor warrior. Every guardian of a planet carries a Sailor crystal within them.
Thus, Sailor Mars, Sailor Venus, and all the other Sailor warriors have their own Sailor crystals that they carry within them. Sailor Moon carries the Silver crystal, Mamoru the Gold crystal.
Only those who are considered successors of a planet can carry a crystal within them. Mamoru is the reincarnation of Prince Endymion. He is the Prince of Earth during the Silver Millennium, which is why he is the rightful Prince of Earth.
Thus, Mamoru counts as one of the Sailor warriors and is the protector of the Earth because he is the successor of a prince. However, he is still not an own Sailor warrior because only women can become Sailor warriors. If Mamoru were a woman, he would be Sailor Earth.
Despite not being a Sailor warrior, Mamoru has the same duties and responsibilities as the other Sailor warriors. It would be interesting to know how powerful he would be if he were a woman. MeinMMO has actually created a ranking of the strongest Sailor warriors: Sailor Moon: The 5 most powerful warriors in the anime
