Many words spring to mind at the thought of Kaioh Michiru, whose other identity is the elegant Sailorneptune. Some of these words would be "sophisticated... brilliant... beautiful... talented... sensitive..."
Are you getting an idea of what this woman is like?
Michiru-san is, in a word, perfect. She can play the violin (and the cello, it seems) as skilfully as a concert virtuoso. In fact, she held several concerts which drew large crowds of people. She also was a student at Mugen Gakuen (Infinity School), an exclusive private school for genius-level students. (After it was destroyed, she attended Juuban high with the rest of the senshi.) She also seems to be very rich, since she owns her own helicopter, etc...
Physically, she is absolutely gorgeous, with huge sea-green eyes and a slender, graceful body. She also has a cloud of aqua-green hair that creates a halo around her lovely, serene face.
Michiru likes pretty things. At one point (Act 39), she buys flowers to decorate her home; she was also a trifle upset when little Hotaru broke her designer plates (Lalique and Royal Copenhagen, if you must know). But she didn't yell at Hotaru or anything; Michiru is very good at keeping her temper. There was one notable exception however; when Kou Yaten insulted her choice of lipstick color, Michiru became rather upset.
You'd think that a talented, beautiful girl like Kaioh Michiru would have the men flocking from everywhere to fawn over her, and hope for her to notice them. They do. Does she care? Apparently not; although she is polite enough to them, they cannot win her heart. After all, she has Haruka. And Tenoh Haruka, it would seem, is the only one she wants. (This doesn't stop Haruka from being a little possessive. It's really quite funny to see Haruka get jealous of Michiru's admirers and drive them off.)
Michiru is the reincarnation of Sailorneptune, the senshi ruling the oceans. She carries the Deep Aqua Mirror, one of the three talismans; by looking into the mirror, one can see the truth. Her powers have a lot to do with the sea as well; she seems able to sense when the sea is angry or disturbed, and her attacks range from "Deep Submerge" to "Submarine Reflection," as well as "Submarine Violin Tide." Mythologically, the Roman god Neptune controlled the oceans.
The Japanese translation of Kaioh Michiru's name fits her character beautifully, too. "Michiru" translates to "rising" (like ocean tides?), but it could also mean "complete" and "mature," and indeed she does seem to be the most mature and perfect of all the senshi. (SM fans are divided as to whether they should love her or hate her for this. On the one hand, it's admirable; on the other hand, it's pretty annoying.) Her surname "Kaioh" means "ruler of the sea," which is an indication of her range of expertise as a senshi. It's also related to the kanji for the planet Neptune, "kaiousei."
In the time of the Silver Millenium, Michiru was the Princess Neptune. (It's very easy to imagine her as a princess, isn't it? Graceful... beautiful... dignified... yep, a perfect princess.) However, she and the other outer senshi were rather solitary people, and did not socialize much with the people of the inner solar system. (i.e. from Jupiter onward in to the Sun.) Their purpose was to keep invaders out of the solar system, and they tended to stay on the outskirts of things. They were very asocial people, and kept apart from the inner senshi. This created problems when they reawakened... but the friction between the two groups was straightened out by the ever-loving heart of Sailormoon.