Setsuna is the oldest and most mature of all the Senshi. She usally guards the gates into the time warp, all by herself. She has the power to stop time temerarily, but will kill herself if she ever breaks that taboo. Chibi-Usa is a close friend of Setsuna's, and was the only one who came to visit her at the gates to the time warp.(Chibi-Usa usally calls her "Luna-P")Setuna in the manga desparetely wants to fight with the other senshi, but can't because of her duties at the gates of time. She is also in love with King Endymion in the manga.

Unlike the other memebers of the Outer Senshi, Pluto first apered in season R, she was the person who befriended Chibi-Usa and sent her to the past. In the manga Chibi-Usa stole the time key from her and went to the past. (The other members of the Outer Senshi apeared one season later in season S)