Neptune was a Senshi before she knew her she'd have a partner, Uranus, maybe even before the Inner Senshi had become Senshi. She was friends with a girl named Elza Grey, who raced at the track with Haruka. Michiru knew who Haruka was before she realized she was going to become Uranus. It isn't said how long she did so, but she followed Haruka around, learning all about her. She was very happy when she did learn that she was going to be her partner. When she met Haruka face to face, thanks to Elza's help, Haruka was cold to her. When Haruka was attack by a daimon, however, Michiru came just before she could grab the henshin pen that appeared, and transformed into Neptune to save her. After being attacked, Neptune told Haruka about how she'd followed her, and Haruka took the pen. Haruka became her partner as a Senshi, and her lover as well, moving into an apartment with her. Their mission as Outer Senshi was to protect the Earth from outside invasions, but at the time the thing they focused on was finding the Talismans to summon the Holy Grail, saving the world from the Dark Messiah [note: in the manga, they had their Talismans already]. They didn't realize it, but they were actually the ones with two of the Talismans. She attends Mugen Gakuen with Haruka.
In both the anime and the manga, Michiru is friendly, slightly arrogant, mature, and incredibly intelligent. She plays the violin professionally, performing many concerts, and has earned a very large amount of money from doing so. She and Haruka often makes flirtatious remarks to each other and exchanges knowing "looks.". She is incredibly close to her [they are lovers, after all], and though they place great importance on their mission, Michiru would sacrifice herself to protect Haruka. She, along with Haruka and Setsuna, raise Hotaru, in the manga after her father dies, in the anime when he is injured and after Setsuna takes Hotaru away from him. She's rather maternal and enjoys looking after Hotaru.
In the anime, Michiru also paints, and doesn't seem to mind the Starlights too much, at least compared to Haruka. She (and Haruka) have to search for the Talismans. She gets irritated sometimes with Haruka's flirting.
In the manga, Michiru is slightly more irritable, and while at first she accepts the Starlights, she gets rather pissed when Yaten insults her and tells Haruka that they need to get rid of them. She and Haruka only pose as Mugen Gakuen students; they infiltrated the school to find the Death Busters. She already has her Talisman.
Michiru has wavy, seagreen hair, in the manga it falls to her waist, but in the anime it's barely to her shoulder blades, sometimes only to her shoulders [easier to animate??] She has blue eyes and has both ears pierced, wearing various different earrings in them. She's about average height and always dresses up. In the anime, she wears some unusual outfits [i.e. episode 101, that magenta number... ick.]
As Neptune, her powers deal with the sea, and her Talisman, the Aqua Mirror, lets her see the truth. Her fuku is seagreen with dark blue bows, her shoes having small heels and with laces similar to ballet shoes. She has no stripes on her costume until she's in Super form, and has a gem with some silver things around it on her choker. She has shorter gloves than the Inner Senshi.
Michiru's really nice, and I think it's cool that she's into art and the violin. Haruka and Michiru are a really cute couple. Other than that, she doesn't strike me as being as great as the other Outer Senshi. I just don't know about her! ^^;; I mean, she plays great music, makes neat pictures, she's kind and pretty and all that stuff, but... there's just not that much going for her that I really, really like. I dunno, maybe it's because she's strangely similar to me in many ways o_O
Senshi Name: Sailorneptune