Tomoe Hotaru, also known as Sailor Saturn, first appears in the Infinity arc of the manga and the Sailor Moon S season of the anime.

Name: Tomoe Hotaru
Meaning: Firefly of Earth
Birthday: January 6
Astrological Sign: Capricorn
Blood Type: AB
Hobby: Reading
Sports: Table Tennis
Favorite Color: Purple
Favorite Class: World History
Least Favorite Class: Gym
Favorite Food: Nihon Soba
Least Favorite Food: Milk
Hopes To Go To: Florence
Fortune Tells: Flower Fortune Telling
Bad Habit: Hangs head
Skilled At: Wound treatment
Weak Point: Marathons
Favorite Stone: Flourite
Seiyuu: Minaguchi Yuko

Hotaru is the daughter of Professor Tomoe Souichi. Hotaru attends Mugen Gakuen, of which her father is the principal and founder. The 12-year-old Hotaru is a very sheltered child; she is usually quiet and reserved. Physically, she is very pale, sickly, and weak. Hotaru has the strange ability to heal small wounds, but she also frequently attacks people without knowing it. Because of her powers, people fear her, and she has no friends. In actuality, Hotaru's dark side is the result of some other thing that inhabits her body.

Her father, Professor Tomoe, is a scientist. In the anime, an explosion in Tomoe's lab (as a result of the alien Death Busters entering this galaxy) took Hotaru's life; a daimon appeared and offered to save Hotaru in exchange for control of Tomoe's body. Souichi accepted the proposition. The newly possessed Tomoe then began cultivating the Messiah of Silence within his daughter. In the manga, after being rejected by the scientific community, Tomoe simply became evil-mad. After a fire killed his wife and nearly killed Hotaru, Tomoe experimented on Hotaru in an attempt to make her a perfect superhuman. In both the anime and the manga, Mistress 9, the Messiah of Silence, lives inside of Hotaru and causes her to unknowingly hurt other people.

Hotaru makes her first and only friend in Chibi-usa. In the manga, during a visit from Chibi-usa, Hotaru has a seizure, and only Chibi-usa's ginzuishou can make her feel better. Mistress 9 then targets the ginzuishou as an energy source.

Uranus, Neptune, and Pluto have been monitoring Hotaru, who they know is the reincarnation of Sailor Saturn. They tell the Sailor Team that they have to kill Hotaru, as Saturn is the soldier who will destroy the world if she brings down her Silence Glaive. Upon learning this, Chibimoon runs off to find Hotaru. However, a possessed Hotaru attacks Chibimoon and grabs her ginzuishou, and Hotaru transforms into Mistress 9.

Mistress 9 causes a lot of havoc, but Hotaru's spirit remains alive inside of her. Hotaru protects the spirit of Chibi-usa and the ginzuishou. Hotaru manages to see Chibi-usa one last time before Mistress 9's body turns into Master Pharaoh 90. After Sailormoon "sacrifices" herself, Sailor Saturn is reborn and attacks Master Pharaoh 90 with her Silence Glaive. Saturn uses "Death Reborn Revolution" on the enemy, and she then swings down her Silence Glaive to destroy the world. Pluto, though, uses "Dark Dome Close" to seal away both Saturn and Master Pharoah 90. Saturn is then reborn as baby Hotaru, whom Neptune, Uranus, and Pluto decide to raise.

In the Sailor Moon S anime, Uranus, Neptune, and Pluto also try to kill Hotaru, who is the reincarnation of Sailor Saturn. Saturn's rebirth means the end of the world, so the Outer Senshi can't let that happen. Chibi-usa tries to stop them from attacking Hotaru, and Sailor Moon saves her and Hotaru from death. Hotaru is then taken by Kaolinite. Eventually, Kaolinite captures Chibimoon and gives her heart crystal to Hotaru, who swallows it and transforms into Mistress 9. Hotaru's spirit is subdued for a while, until Mistress 9 tries to get the Holy Grail from Sailor Moon.

After Mistress 9 successfully tricks Sailor Moon into handing over the Holy Grail, Hotaru's spirit resurfaces. She manages to overcome Mistress 9, but her body is destroyed, and Hotaru becomes Sailor Saturn. Saturn goes off to fight Master Pharaoh 90 with her Silence Glaive. Super Sailor Moon follows her, and once Pharaoh 90 is defeated, Sailor Moon appears with baby Hotaru in her arms. Haruka and Michiru return baby Hotaru to Souichi, who has been released from the daimon's control.

In the Dream arc of the manga, Hotaru is the "princess" of Haruka-papa, Michiru-mama, and Setsuna-mama. After the Dead Moon's solar eclipse, she starts to grow and mature rapidly from a baby to about a ten-year-old girl. Hotaru eventually awakens to her nature as a Sailor Soldier again, and she gives her parents power-ups to transform. She then leads them to the Dead Moon Circus, where the four Sailor Senshi join the fight against Neherenia.

Hotaru does not appear at all in the SuperS anime. However, in the Neherenia arc of the SailorStars anime, Hotaru has a similar life as she does in the Dream manga. Taken from Souichi by Setsuna, she manages to save the Outer Senshi from Neherenia's Mirror Paredories even though she's only a baby. Hotaru gives them their power-ups, and she ages into a toddler. Afterwards, Hotaru is raised by the Outer Senshi and grows rapidly under their care until her senshi nature awakens. The soldiers then save the Sailor Team, and Saturn tells all the senshi to give their power to Sailor Moon so she can transform into her ultimate form, Eternal Sailor Moon. Saturn and the other senshi then go after Sailor Moon to save Mamoru and defeat Neherenia.

Once Neherenia has been returned to the past, Hotaru does not appear in the anime for a while. She is finally brought back very late into the story so that her Star Seed can be harvested by Galaxia. Actually, it is Uranus and Neptune who, while pretending to be evil, kill Saturn and Pluto. Saturn is later brought back to life after Chaos' defeat.

In the SailorStars manga, Hotaru serves pretty much the same purpose as she does in the SailorStars anime - as a soldier ripe for sailor crystal plucking. However, for the early part of that arc, she is a cheerful, active elementary school student. She attends the same school as Chibi-usa.

• Death Reborn Revolution: Lots of ribbons come out of her Silence Glaive. Manga only.
• Silence Glaive Surprise: A destructive attack. Used in the Dream arc of the manga and the SailorStars anime.
• Silence Wall: A protective barrier from her Silence Glaive. Used in the Dream arc of the manga and the SailorStars anime.
• Saturn Crystal Power, Make-Up: Manga only. Hotaru transforms into Super Sailor Saturn.

I like Hotaru as a little girl the best, in the Dream arc of the manga and beyond, and the SailorStars anime. She's absolutely adorable as a child, and she completes the Outer Senshi family model so well. Otherwise, Hotaru is extremely sweet, but she's not really a character I find that interesting.