Setsuna Meioh

Setsuna Meioh is the civilian identity of Sailor Pluto.

Personality
Setsuna Meioh is a college student while the others are still in middle or high school. Setsuna never assumes any type of official leadership role. Even among the Outer Senshi, she frequently defers to Sailor Uranus and Sailor Neptune.

She often maintains a stoic persona, intent of maintaining law and order. However, she is shown to have a special relationship with Chibiusa, acting as a surrogate mother.

Appearance
Setsuna is a young adult woman who has knee length dark green hair with some in a bun and the rest hanging down freely, and red eyes. In comparison to the other Senshi, her skin is darker.

Some depictions give her lighter skin and change her eye color from red to purple.

Sailor Moon
Setsuna, as Pluto, was the guardian of the Space-Time Door for millennia. She had three taboos that she was not allowed to break as a result-- She must never leave her post, she must not allow anyone to travel through time, and she must never use her powers to disrupt the flow of time in any way. Breaking the last taboo would mean the end of her life.

Sweet Guardian Sailor Cookie
Sailor Pluto appears as a vision to Kukki Kobayashi while she's returning home from school, requesting help. Explaining that there are discrepancies within the past that could affect the future negatively, Pluto reveals that she has chosen Kukki as a new Sailor Guardian to go back in time, investigate, and stop the future from changing. Giving Kukki a transformation pen, Pluto sends her into the past (specifically the events of the Black Moon Arc), and remains as a mentor to the new soldier.

Arc 1
Setsuna is mentioned in Act 3 and 4, then makes a first appearance as Sailor Pluto in Act 6, as a hologram from Kukki's transformation pen. Kukki questions her mission, to which Pluto reveals that there are two Sailor Soldiers that shouldn't be in the timeline-- Sailor Stellar and Sailor Galaxy. Cautioning Kukki, the hologram then disappears.

Pluto makes a physical appearance in Act 8, confronting the Inner Soldiers (besides Usagi, who had been kidnapped by Demande) and Tuxedo Mask for being within the corridor of Space-Time, but her attack is interrupted by Chibiusa, who apologies profusely for stealing the Time Key. Though she scolds Chibiusa for a short moment, Pluto embraces her and expresses her relief and gratitude to Chibiusa and the Inner Senshi. She then opens the Door of Space-Time and allows the group to go to the 30th Century, but remains at her post, as it is taboo to leave.

Trivia

 * She is the only Senshi to invent a civilian identity.
 * She is also the only one of the Solar System Senshi to invent a Sailor Soldier identity for someone, that being Sailor Cookie. The only other character to do this is Guardian Cosmos.
 * She bears a striking similar resemblance to Tsuruyo from the Haruhi series.
 * What is ironic is that Kukki Kobayashi, Setsuna's best friend, looks similar to Mikuru Asahina, and Tsuruyo and Mikuru are best friends, just like Setsuna and Kukki.