Michiru is formally introduced in the third story arc, although she appears in silhouette alongside Sailor Uranus in episode 89, a "teaser" to Sailor Moon S.

She is portrayed as a very polite, calm character in the series. She dislikes being patronized even if not doing so would hurt her feelings, and subsequently will not indulge people. This is alluded to in her backstory, explaining that she was congenial but generally not social. Michiru is also graceful and delicate, with an aura of sophistication. She is clearly intelligent, and this usually manifests itself through art and music. Usagi (to whom this observation is especially relevant) once commented that Michiru was the ideal example of a princess.

Michiru attends Infinity Academy with Haruka (and the younger Hotaru Tomoe) when she is first introduced. In the manga, after Infinity is destroyed, she and Haruka later attend the same high school as Usagi and the other girls. It is never mentioned where they go after this in the anime, but the two of them are shown driving away in their last appearance in Sailor Moon S, and during a made-for-TV special set during the following season, they are shown staying at a hotel elsewhere in Japan. According to the musicals, Michiru had experience studying abroad.

Michiru's closest bond is with Haruka, and Takeuchi has explicitly stated that the two are in a lesbian relationship in both the manga and the anime as well as the musicals.

In the anime, Michiru briefly flirts with Kou Seiya, at that time a man, asking him to help her unzip her dress. Her stated intention, earlier in the episode, is to learn Seiya's motives out of fear that he is a threat to the planet. This flirtation does not occur in the manga, where Seiya is always a female and plays a much more minor role. However, in the Infinity arc, Michiru appears as temptation for Mamoru, paralleling Haruka being used as temptation for Usagi. Though she never makes any of the advances on Mamoru that Haruka makes on Usagi, Usagi is jealous of her because she sees them together.

In the dubbed anime, her relationship with Sailor Uranus was redefined. In episode 95, Michelle (Michiru) and Amara (Haruka) are stated to be cousins by Amy (Ami), who barely knows them, and are referred to as such for the next few episodes. Thereafter, however, much of their flirting inexplicably continues. In one episode, they claim to have known each other all their lives, but a flashback to their first meeting (in the very recent past) is shown shortly thereafter. By the time the "S" series was released in English, many fans were already familiar with the characters and their relationship, so their treatment as family members is mostly ignored.

In episode 92, where the two flirt gently in the original, the dub changes their dialogue to a banter about love at first sight, and inserts the statement that Michelle does not believe in romantic love. In episode 94, Michelle talks about her first kiss with Brad, "the cutest guy in the school," where the original text was about the first kiss ever, between Adam and Eve. She later says, "My sweet Brad... I wonder where he is today," further defining her as heterosexual.

Michiru is deeply artistic and is the Senshi most associated with the arts. Her known skills include the violin, swimming, and painting; of all her skills, her strongest is as a violinist, which is also her greatest dream. She likes all her classes, especially music, and belongs to the Music club at school as well as the Swimming club. In the manga, she collects cosmetics; in the anime, she loves to swim, often using the water as a way to relax. Her favorite food is sashimi, while her least favorite is kikurage mushrooms. She also dislikes sea cucumbers for unclear reasons, and her favorite color is Marine blue.

Special powers and items

In her first Senshi uniform, Sailor Neptune demonstrates her ocean-based powers with Deep Submerge.Even in civilian form, Michiru has some precognitive gifts, as she occasionally states that "the sea is stormy" when there is an evil presence at work. She is not shown using any other special powers in her civilian form, and must first transform into a Sailor Senshi by raising her hand or a special device into the air and shouting a special phrase, originally "Neptune Planet Power, Make-up!"[17] In the manga she eventually gains her Neptune Crystal and this phrase changes to evoke Neptune Crystal Power.[18] In the anime, although she does upgrade to Super Sailor Neptune, the Crystal is never mentioned and her transformation is never shown on screen after the upgrade.[19] Her transformation sequence involves a pillar of seawater encircling her body and swirling around her as her uniform appears.Sailor Neptune's powers are inspired by Roman mythology, where Neptune is the god of the ocean. She never uses the element of water in a general sense, that being Sailor Mercury's domain; instead, she draws energy from the "deep waters" and blasts this at her foes (rather than attacking with physical ocean water). She is given three major attacks in the series, and although they all have English names (like those of the other Sailor Senshi), each is also given kanji in the manga to denote the meaning to Japanese readers. For example, her first attack, Deep Submerge,[20] is given kanji which translate precisely to "deep" (深?) and "submerge" (水没?).[21] The intended English pronunciation is given in furigana. This is Sailor Neptune's primary attack for most of the anime series.In the manga, Michiru owns a special hand mirror which supplements her precognition.[22] This turns out to be the Deep Aqua Mirror, one of three powerful Talismans, the other two of which are carried by Sailor Uranus and Sailor Pluto. In the anime, she does not gain the mirror until she is revealed as one of the Talisman bearers;[23] in either case, it is used in her second attack, Submarine Reflection[24] (深海鏡射?, "deep sea mirror shoot").[21] In the anime, Michiru can use it through and dispelling illusions, as seen in the Supers movie. In the manga, she can use it for astral projection,[25] and lends it to Chibiusa while she and the other Outer Senshi are away. Chibiusa invokes the mirror's power by stating its name and is able to teleport to Sailor Neptune's location.Michiru's violin, a Stradivarius worth some five million dollars, is called the Marine Cathédrale and is named after "the temple of the sea".[26] Aside from playing it in concert, she uses it in her third and final attack, which (like the instrument itself) has a French-inspired name: Submarine Violon Tide (深海提琴潮流?, "deep sea violin tide").[27]The Neptune Crystal is perhaps her most important possession, as it is her Sailor Crystal and the source of all her power, which becomes especially important in the fifth story arc. It is given to her by Sailor Saturn.[21]