I love guarding the door guarding the door is fun :)
—Sailor Pluto
Sailor Pluto is a member of the Sailor Guardians whose job is to guard the door. That's it—she just guards a door because that door might be able to travel through time.
Sadly one day, the planet her name is based on became classified as not a planet, so guess what happened? That's right—she was brutally murdered by Luna, and her corpse was left to rot. Until Sasori revived her as a reanimated puppet, and she was forced to guard the Akatsuki hideout's door while her body was slowly falling apart. She would later develop symptoms of nihilism and self-hate as she believed she failed her fellow Sailor Guardians and cried in a corner over it. She even started to remember her death at the hands of Luna, which caused her to develop PTSD whenever she sees a cat.
One day she was kidnapped by Cinder, and after using the banned spells of necromancy, Sailor Pluto began convulsing and returned to living in her mortal form. Pluto wondered why this was happening, and the man on fire explained to her that she had been chosen to be the guard for the Unbeatable Palace.
Pluto was kinda happy, but her sadness would slowly take over her. She began cutting herself while repeating the phrase "WHY WON'T THAT CAT LEAVE ME ALONE!" This would later catch the attention of Yuugi Hoshiguma, who would later bring up this issue to Super 17 and the rest of the crew.
It seems that Pluto has basically become an emotional wreck who can't be trusted around sharp objects, and Yuugi decided to become a mother figure to Pluto in order to stop her from cutting herself. But her insecurities would catch up to her every time she looked at the scars. She thought that she became a freak and ruined her body and thought that nobody loved her, but she knew that it was all a lie and decided to go back to the Sailor Guardians in order to pay a visit to her friends.
Moon and everyone else was concerned for her mental state, so Moon decided to prescribe her with The daily dose, which suppresses the thoughts of self-harm and suicide. Pluto thanked her friends before returning to the Palace, where she spent most of her time either having fun with the other members or guarding the door. She misses being a part of the Sailor Guardians, though, and frequently invites them over to the palace once a month. She's a very nice person, but all that self-hate held her down. In the end, she did redeem herself, but will have frequent schizo-like outbursts whenever she sees a black cat.