Noteworthy Manga Facts

Sailor Pluto is the solitary guardian of time, she was placed in her position at the Gates by the Moon family a very long time ago - by the old Queen Selenity (Usagi's mother). When she dies, after stopping time, she is reincarnated, is still a Sailor Soldier, but now has an Earthly identity as Setsuna Meioh. Below are some interesting and noteworthy manga facts about the Soldier of Revolution.

Sailor Pluto's Age
Sailor Pluto has had a longer life than anyone. She has lived through every era, so she has extremely wise judgment.

Pluto's Mission
Sailor Pluto's mission and situation are entirely different from that of Princess Selenity's four guardian soldiers. She carries the blood of the god in charge of time, Cronos. She lives between time, the solitary guardian of the door of the underworld. Since ages ago, the space-time door has been off-limits, and Sailor Pluto was the one who enforced that."

As Guardian of the Time Gate, she carries many keys with her on a belt around her waist. Her garnet rod is her weapon and that, too, is shaped like a key, and is described as such in Manga Act 18.

Physically
Setsuna is a tall woman, with flowing dark green hair. Before her reincarnation, she was always a little depressed. Setsuna is also a dark skinned woman. In the manga, Act 18, Sailor Pluto speaks to Small Lady/Chibi Usa and it is narrated in this way in the manga:

"Small Lady," says the sailor-suited woman. She holds an ornate staff. Her dark hair flows back over her dark skin. "The highway of time isn't allowed. Using it, or even knowing about it is strongly forbidden."

"Stop!" a voice calls. "From here is the future. You cannot proceed." The woman steps forward. She carries a long staff resembling a key. A sailor suit covers her dark skin. Her dark hair blows in the wind. "I am the watcher of the space-time door, the guardian of the underworld. I am Sailor Pluto! And I will eliminate those who violate the law."

It is under debate whether she is "black/African" or just of a deep olive complexion, but many manga pictures, artbook images, and the manga itself reveals she is dark skinned.

Family
Other than the Sailor Senshi, Setsuna has no real family. But Naoko's Bishoujo Senshi Sailor Moon is richly based on Greek Mythology and we learn that Setsuna's father is Chronos/Cronos - the one leader of all the Gods who was overthrown by his son Zues. Act 18 of the Manga below is the evidence:

She raises her key into the air. "Time Guardian! Tear apart the sky, and open the space-time door to me! I call the true name of the almighty god of time, the time guardian's father! Chronos! Reveal to me the path of light!"

Setsuna's/Sailor Pluto's Closest Friends
Chibi Usa/Small Lady
Chibi Usa is the only person, other than Neo-Queen Selenity, who goes to visit Pluto often at the Time Gate. Chibi Usa is able to make Pluto laugh and smile. It is obvious throughout the manga, how greatly Pluto cares for Chibi Usa and how devoted she is to her as the Princess. She is also the one who taught Chibi Usa this phrase, Abracadabra - the magic words that would life Chibi Usa's spirits.

Neo-Queen Selenity
Selenity/Sailor Moon is everything in the world to Setsuna/Pluto. To protect her, server her, and fight with her is her one goal and purpose in life. To be by Neo-Queen Selenity's side - it is what Pluto longs for. After Pluto's first death, Neo-Queen Selenity reincarnates her and sends her to the past to fight with her past self, Sailor Moon. Pluto is overjoyed at this and when she is reincarnated, it is commented that this Pluto is stronger, taller, more focused than ever before.