At school, she is bullied because of her constant sickness which is revealed to be hosting Mistress 9.

Saturn gives her host the memories of her previous life and reawakens her as Super Sailor Saturn, the Sailor Guardian of Death and Rebirth. Hotaru mainly appears to have a black shoulder-length bob with purple shine on front and purple eyes. She can easily obliterate entire planets and reduce them and their inhabitants to complete oblivion. However, Hotaru suffers from fits obtained from a lab accident years ago, so she sometimes collapses in pain. Her spirit is housed within Hotaru Tomoe (土萠 ほたる, Tomoe Hotaru), who closely resembles her.

Days later after Sailor Moon retrieves the Holy Grail, she and Chibiusa go to the park. They started to realize that she could be the Messiah of Silence. When influenced by Super Sailor Saturn, Hotaru is very determined when it comes to her mission and her duty as a Super Sailor Guardian, and her personality is very different from her human identity as Hotaru Tomoe, as she partially possessed and influenced by the spirit of Sailor Saturn herself. Her skirt became two-layered, the top layer being purple and the bottom lavender. She can also erect force-fields around herself and others that can withstand even Galaxia's strongest attacks. As Princess Saturn, she dwelt in Titan Castle and wore a dark purple gown with gloves—she appears in this form in the original manga and supplementary art. Hotaru's body was under the control of the Messiah of Silence, passing orders to Professor Tomoe. Hotaru is later reborn as a baby and raised by Haruka, Michiru, and Setsuna as her adoptive parents.

As Sailor Saturn, she retains her civilian appearance but also wears a gold tiara on her forehead with a white gem on front. She later expels the evil entity out of the universe where she instructs Sailor Pluto to open the Gate of Time and have it close with her for rebirth to be possible.

Chibiusa was eventually captured by the Death Busters and the Messiah of Silence consumed Chibiusa's Pure Heart Crystal, changing her form into Mistress 9. Her school uniform consists of a red top, green skirt, and blue pantyhose. Her belt consisted of two ribbons, one purple, and one lavender, with two long, thin back ribbons, clipped together by a golden five-pointed star. As the strongest and most feared of all Sailor Guardians, Saturn has powers related to death and destruction, silence and ruin themselves. The spirit of Sailor Saturn meets the reborn HotaruChibi Moon stopping Saturn from using Silence Glaive Surprise.Take your favorite fandoms with you and never miss a beat. She also wields the Silence Glaive while in this form. Usagi sees them and remarks that they are acting very friendly. The latter became close friends. Sailor Pluto revealed that Hotaru was the reincarnated Sailor Saturn, and feared that if Saturn awakened, she would end the world. Her tiara gem was a purple five-pointed star and her earrings were dangling, purple five-pointed stars. While possessing Hotaru's body, Mistress 9 struggled to keep control as Hotaru continued to fight for control. In the fifth chapter, she gets killed along with Sailor Pluto and revived in her Eternal Sailor Guardian form to kill Sailor Moon, thanks to the efforts of Sailor Moon, she gets revived. She had the regular shoulder pads with translucent parts, and the back waist bow was enlarged and lengthened. After Mistress 9 awakened with Pharaoh 90 to make Tokyo the new Tao System, Sailor Saturn later awakened when the Sailor Guardians attacks did not hurt the evil entity. When she transformed into Eternal Sailor Saturn, her choker was V-shaped and the center of her front bow was a lavender five-pointed star in her maroon front bow. He also connected with She is shown as a daughter to Souichi Tomoe and is a sixth grader at the Mugen Academy. Like Trista, little is known about Sailor Saturn's lifetime before or after the Negaverse and Queen Beryl destroyed the Moon Kingdom and killed its subjects. Her gloves became longer, reaching her upper arms. Days later after Sailor Moon retrieves the Holy Grail, she and Chibiusa go to the park. Her front and back bow is either dark brown in her anime official art or black in the near end of the anime's 3rd season both her silver star brooch and the star gem on front of her choker resemble the pure heart crystals being recently hunted by the Death Busters and wore a matching silver planetary dangling earrings on both of her ears as her main earrings closely resemble the planet Saturn. It is assumed that she may have been present during the attack or killed and reborn by some other means. In her initial appearance, she was usually seen in her casual attire or sometimes wore a winter jacket while in Mistress 9's control. Her shoulder pads were large lavender puffs with two patches of purple fabric attached to the bottom. Hotaru is a petite girl with short dark purple hair, violet eyes, and pale skin. Her boots were knee-high and white, and each had a purple V-shaped border with a golden five-pointed star at the top. She was among those given the duty of protecting the galaxy's Outer Rim. Pharaoh 90 was destroyed and Sailor Moon survived, holding an infant Hotaru in her arms. After Mistress 9 opened the way for Pharaoh 90, Hotaru was finally able to regain control and destroy Mistress 9, reawakening as Sailor Saturn. Hotaru meets Chibiusa fighting a Daimon.

Hotaru is still an innocent girl without any memory of her previous life until she is visited by her alter ego, Sailor Saturn. Chibiusa loses her hat at the park and runs to retrieve it, where she first meets Hotaru. Sailor Saturn is a member of the Sailor Guardians of the Moon Kingdom during the Silver Millennium eras, supernatural reincarnations of planets and stars who protect the Solar Systemfrom evil.