Setsuna Meiō (冥王せつな?) is Sailor Pluto, she`s gurdian of time.
Pluto's first appearance is during Sailor Moon R, where she watches over Chibi-Usa in the past. She has a very special relationship with Chibi-Usa. She is the keeper of the Garnet Orb.
Setsuna is the oldest of the nine Sailor Senshi; in the R season, she is a college student while the others are still in middle o high school. Despite being the eldest, Sailor Pluto never assumes any type of official leadership role. Even among the Outer Senshi, she frequently defers to Uranus and Neptune.