Michiru Kaiou

Kaiō Michiru

Japanese: 海王みちる
Romanji: Kaiō Michiru
Aliases: Sailor Neptune, Super Sailor Neptune, Eternal Sailor Neptune, Princess Neptune
Residency: Tokyo, Japan, Moon Kingdom, Crystal Tokyo

Student, violinist
Cooking teacher (Parallel Sailor Moon only)
Sailor Senshi
Outer Sailor Senshi of Silver Millennium
Outer Sailor Senshi of Crystal Tokyo
Princess of Neptune


Haruka Tenou (Boyfriend)


Solar System Sailor Senshi


Moon Kingdom, Crystal Tokyo

Birthdate: March 6 (♓)
Age: 16-17 (S), 17+ (Stars)

163 cm or 5'4"

Gender: Female
Species: Human
Blood Type: O [1]
Likes: Collecting cosmetics, playing the violin, swimming, painting, music, sashimi, aquariums, the colors turquoise, teal, and aquamarine
Dislikes: Sea cucumbers, kikurage, physical education
First Appearance
Manga: Act 27 - Infinity 1, Premonition
"Protected by Neptune, the Outer Planet of the Seas, Guardian of the Deep Sea, I am Sailor Neptune. "
— Sailor Neptune's introduction

Michiru Kaiou  is the civilian identity and present-day incarnation of Sailor Neptune.

Nomenclature & Etymology


Michiru's surname (海王, kaiou) translates to "Sea King", based on the Japanese name of the planet Neptune (海王星 Kaiousei "Sea King Star", the given title of Neptune, the Roman god of the sea).

Michiru's first name means "rising".Her original English name Michelle a French feminine form of Michel, from the Hebrew name Michael meaning "Who is like God?"Her name that was used on the doll box back in the 1990's used by Irwin was Nerissa which means Sea Nymph/From the Sea.



Michiru is an extremely beautiful and delicate-looking girl of slim stature and average height, with deep blue eyes and wavy teal hair that falls just past her shoulders. The epitome of elegance and femininity, she has an excellent sense of fashion, being always dressed smartly, and applying makeup or perfectly made up already. Usagi and Minako were both utterly dazzled by her beauty when they first saw her, and Usagi has gone as far as saying that Michiru is exactly what a fairy tale princess would be like.


Sailor Neptune's fuku consisted of a white leotard with a sea-green skirt, a navy-blue front bow, and a navy-blue back bow. The collar on her leotard was sea green and it did not have any stripes on it, and her shoulder pads had three layers. Her gloves were white with sea-green wrist fittings. Her shoes were lace up loose sea green boots. Her accessories were a gold tiara with a sea-green gem in the middle, her earrings were white studs and had some kind of planetary object surrounded by a ring dangling from them, and a sea-green choker with a sea-green gem with golden accents attached to it.

During the Silver Millennium, Sailor Neptune was also the Princess of her home planet and was among those given the duty of protecting the solar system from outside invasion. As Princess Neptune, she wore a sea-green gown with the symbol of Neptune on her forehead. She dwelt in Triton castle.


Elegant, sophisticated, though sometimes cold and capable of sharp anger, she has been described by Usagi Tsukino as 'the ideal princess'.

Michiru attends Mugen Academy with Haruka Tenou and the younger Hotaru Tomoe. She is patient and caring, almost always offering a smile or laugh to a situation. While polite and calm to a fault, she is not the most social person, but when she does become close with someone it is because she truly wants to. She dislikes being patronized and will not indulge others.

This can make her look like a snob, and her seeming perfection at everything does not help this perception of her. She is a genuinely intelligent young woman, a prodigal violinist and artist, already famous for her endeavors. Her intelligence is also apparent through her acceptance to Mugen Academy, a school with a very high acceptance threshold; only geniuses of some field are permitted enrollment.


Senshi Info

Michiru Kaiou can transform into Sailor Neptune by saying Neptune Planet Power, Make Up!



Weapons and Items



Michiru Kaiou

In concept art, Naoko Takeuchi had planned for Michiru and Haruka to be affiliated with the Takarazuka Revue. In addition, she was originally intended to wear a bow in her hair when at school. Neither characteristic was carried over to the final version of her development.

According to the Materials Collection, she had a kindness "as great as the sea."

Sailor Neptune

Sailor Neptune's character was not developed until partway through the Sailor Moon series, after the other Guardian Senshi had already been established. When she was created she was made along with Sailor Uranus, the pair was meant to be "complementary but opposite characters", and were meant to work along with Sailor Pluto from the beginning. Sailor Neptune's visual design is made to evoke images of her element, the ocean. The choice of her colours along with the wavy quality of her hair, which Takeuchi even joked, might be thought of as seaweed hair.


  • Michiru owns her own helicopter that she calls the Kaio Maru.
  • Michiru is capable of using the Deep Aqua Mirror without needing to become Sailor Neptune.
  • Michiru's apartment number in the Infinity arc is "1306". If one removes the "1", they will get "306", the numbers of her birthday. (Michiru's birthday is March 6, or 3-06)
  • As with the other members of the Outer Senshi, her surname is also the name of a rail line in Tokyo.
  • The Sailor Moon "Materials Collection" confirms Haruka to be in her first year of high school at the start of her first appearance, along with Michiru.
  • At the 1998 San Diego International Comics Convention, Naoko Takeuchi confirmed that Uranus and Neptune were indeed intended to be seen as lovers. "Uranus has the heart of a man, while Neptune is more girlish," she said.[2][3]
    • The question "Are Uranus and Neptune really lovers, and if so why did you make them gay?" came from a young female fan who wanted a clear answer. Naoko-san’s answer was that, "YES, they were a couple!"
    • Naoko further commented that Neptune was "feminine" and Uranus "masculine" and joked they had a relationship because "they had lot’s of time on their hands."
    • This relationship was changed in the 1st U.S. dub due to censorship.
  • In a 1996 interview with Animerica magazine, Naoko Takeuchi stated that while "Sailor Moon is closest to me in terms of personality; Sailor Neptune is the opposite."
  • While not named, she was able to use her violin to create an unpleasant sound as an attack on the Senshi.
  • In Greek and Roman mythology, Neptune is the god of the sea.
  • Sailor Neptune's planetary symbol (♆) stands for the trident of the Greek and Roman god.
    • Her planetary symbol shows on the back of one of the Talismans, the hand mirror.
      • It is not known, why Sailor Venus did not get the hand mirror, as it represents her home planet and Roman goddess, but Sailor Neptune.
    • Neptunium is not symbolized by ♆, since in alchemy this planet was not known yet. It only carries the name of the planet.
  • She, along with the other Outer Senshi, possess one of the Talismans needed to summon the Holy Grail and awaken Sailor Saturn.
  • Sailor Neptune is one of the only Senshi (besides Sailor Mars) who possesses exceptionally strong psychic abilities and the only Outer Senshi who has such powers.
  • Sailor Neptune is the second Senshi to use a sound-based/supersonic attack (with her violin), the first being Sailor Moon with her supersonic wails.
    • She is also the second Senshi to use a personal/ordinary item in battle, the first being Sailor Mars with her ofuda.
  • Sailor Neptune and Sailor Uranus are the only members of the Sailor Senshi who's backstory of becoming a Sailor Senshi had never been revealed in the manga.
  • Eternal Sailor Neptune is eliminated and given bracelets from Galaxia in the manga. But in the anime's fifth and last season, she voluntary sells her own heart and soul to Galaxia, and is given her mind-controlling bracelets.
  • Eternal Sailor Neptune is on the cover art of volume eight of the reprinted manga. On the kanzenban manga, Sailor Neptune appears on the cover of volume 6 along with Sailor Uranus.



  1. Michiru Kaiou at Sailor Moon Official Website (Japanese)
Sailor Senshi

Solar System Senshi Sailor MoonSailor MercurySailor MarsSailor JupiterSailor Venus/Sailor V
Other Senshi Sailor Luna
Civilian Identities Usagi TsukinoAmi MizunoRei HinoMakoto KinoMinako AinoLuna Tsukino
Allies Mamoru Chiba/Tuxedo MaskLunaArtemis

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