"Her personality has been described as distant and somewhat lonely, however she does consistently display warmth and affection for Chibiusa. When she reincarnates, she becomes more friendly, but is still not very emotional, although there are moments in the manga where she expresses much more emotion than the anime." -Sailor Pluto Wikipedia

Sailor Pluto's solo should be the most emotional out of all of the senshi. Her part translates to;

 "Even if separated and faraway,
my heart is always by your side"

-Sea of Serenity

You do not have to copy the performer's voices, but rather just mimic the essence of the character's voice. Sailor Moon should be cheerful and bright, Neptune should be calm and mature, etc.

Please use the mic you intend you complete this project with if you get the part. Have your audition be acapella, but in time with with the song. Use the video above to reference the song.