Michiru is the former Princess of Neptune and transforms into Sailor Neptune, whose focal element is water. Interestingly, she shares this element of influence with Sailor Mercury. Her planetary symbol resembles the fork of a trident staff, usually associated with Neptune, the God of the Sea.

Michiru is half of a very dynamic and highly effective partenership with Haruka, Sailor Uranus. At times they seem to alomost change character when they transform, as Michiru is warm and sports a subtle sense of humour whereas Sailor Neptune tends to be cold and logical. This apparent coldness stems from her absolute determination to complete her mission, which she and Haruka must do at all costs. If necessary they would even sacrifice each other to achieve their goals.

This does not in any way reduce the strength of their relationship, however. In the English version they were cousins, but in actual fact they were romantically involved, a fact that they never directly admitted to the other senshi, but most seen past the explanation of them being 'just good friends'. It is partly because of their affection for each other that they are driven so hard to rid the world of the negatives forces which threaten it, and complete their mission.

Being so selfless both senshi have pure heart talismans, in the case of Michiru she has a mirror that allows her to see clairvoyantly and is the source of power for her 'Submarine Reflection' attack.

Michiru is very elegant and lady-like, and has a great love of the arts. She plays violin professionally, and is also a renowned painter. In a perfect world she no longer needs to be a Sailor Senshi, and can concentrate on her music and spending time with her beloved Haruka.