Neptune, also known as Purple Heart, is the main character of the Hyperdimension Neptunia franchise. She is the Console Patron Unit (CPU) of Planeptune. Neptune personifies a fictional Sega console, although her name was inspired by the Sega Neptune, which combined the Sega Genesis and 32X but was never released.

Due to the Neptunia series being a game that revolves around different universes and dimensions, there are multiple Neptune's throughout the series though all of them retain more or less the same personalities and core aspects regardless of the setting.

Personality
Out of the four main Goddesses, Neptune is the most careless and carefree. She'll jump head first into any dangerous situation without consideration, and she does not bother to think about the possible consequences that await. Several characters, including her own friends, see Neptune as stupid and somewhat crazy, due to coming off as a clueless airhead with a tendency of asking random questions or getting shocking ideas and theories.

Besides that, Neptune is easily surprised and has shown klutzy tendencies. She usually shows an eager and perky behaviour and is very affectionate to generally anyone, to the point of giving them cute nicknames or refusing to give them their personal space. Such as tickling girls, hugging them, or even touching their breasts. Noire is her common target.

She also happens to really love food. Often in the middle of a snack or thinking about food, more-so in the Manga and official artwork she can be seen eating every so often. She often receives comments from both friend and foe about her 'pudgy' physique.

At first, Neptune was uncaring for anything important and was very lazy and impatient. She soon learned however that it was important to protect everyone depending on them and made plenty of new friends.

In mk2, Neptune is still an airhead and pretty childish. But she's lost her attitude and impatient behaviour and seems a little more mature and caring, and a little less selfish. She cares deeply for her little sister and tries to help with her confidence issues, and also happens to be very protective over Nepgear.

In Victory, Neptune seems to be the same but she has become somewhat more rude and insensitive, and has picked up her lazy behaviour again, showing that she's never quite gotten over being irresponsible yet.

In the manga adaptation, Neptune is still a friendly, touchy, happy girl whose love of food is a lot more apparent then in the game itself. She also is shown to be a very big pervert, such as near the end of the Christmas chapter when she began to picture a bondage themed Noire and gave her a funny expression until Noire caught her.

In the anime adaptation, her personality remains mostly the same, though she seems slightly less vacuous and tends to take situations, as well as her responsibilities, more seriously than her video game counterparts.

Purple Heart
As Purple Heart, Neptune turns very serious and loses her ditsy attitude and friendly disposition at first. Showing a more confident, mature, prideful self instead. Unlike most, her voice noticeably deepens significantly. She loves a good fight and does not give up until winning. She feels superior to the rest, due to being the strongest in terms of sheer power, making a single hit damage up to 2000 points. The others would have to power up just to make a special attack match that very amount.

Despite this, however, and due to her over-confidence, they teamed up against her and took her down with ease, acknowledging that she was the biggest threat out of the four of them. While she is much more calm and observant, Purple Heart happens to be full of herself at first and gloats how the others couldn't beat her even if all three tried at once. It was her pride and gloating that made her the victim of their termination. Over the course of the game, due to her memory loss, she lessens up on this harsh behaviour.

In mk2 and Victory, Purple Heart is much more level headed and less prideful now and still retains "Neptune" traits in herself. Such as riding a roller coaster despite causing a light panic. She trusts the other Goddesses more than in the first game and is more caring towards the others. When she is sent to the parallel dimension of Gamindustri, she takes on the role of leader and usually acts as the voice of reason when the other CPUs lose focus of the situation to indulge in their eccentricities and arguments.

Like her normal self, Purple Heart still has a bit of air-headed tendencies. Though, it is a far less prevalent trait of her personality when compared to her human self. Also, Purple Heart has traits as a normal teenage girl. For example, in a drama CD, when a spider suddenly comes out, she becomes very frightened and screams. In a another CD, during a confession, she claims she's like a normal girl because she falls in love easily if she is treated by kindness and how they (the person she likes) have been always by her side. A scene with Steamax also caused her to shriek like one upon seeing a erotic scenes that he had cut up.

Appearance
Neptune is a fair skinned girl with light purple eyes and a matching shade of hair. It's shoulder length with somewhat messy bangs with many strands sticking up and few framing her face. She wears two gamepad-shaped hairclips. Originally Neptune's measurements were 73b (an A cup), 54w, and 76h. She is 146 cm (4 ft 9 in) tall and weighed 37 kg (83.79 lbs). In mk2, Neptune has gained a little bit of weight. (Side note: apparently she has cute jiggly thighs.)

Originally Neptune wore a big white hoodie-like dress with purple striped cuffs, lining, and a purple hood. The outfit had pale, ice blue and light lilac accents. As well as a zipper section, two big round pockets, a big zipper with an N on it, and strings resembling a plug. Around her neck she wore a simple white choker. Her lilac shoes have blue and white accents and were also worn with blue and white striped stockings. When revealed, her under garments consists of blue and white stripes.

As Purple Heart, her hair becomes a dark lilac-purple while her eyes turn blue. Her hair becomes very long and is worn in twintail braids while her bangs and the hair that frame her face are somewhat longer. Her hairclips turn into small black circular pieces with glowing blue x's on them. Her figure is more mature/curvier, only losing out to Vert/Green Heart (and in Neptunia V, Iris Heart and Yellow Heart) Purple Heart's suit resembles a black skintight leotard with purple segments and silver pieces along it. The boots/leg armour is above the knee. Her measurements originally were 85b, 58w, and 84h. She weighed 48kg and was about 164cm tall. In MK2, her breast size had increased from a D cup to an E, while her hips increased one size.

In Hyperdimension Neptunia V, Neptune's new attire looks like a summer variety of her previous outfit. Instead of a big sweater/hoodie dress, she wears a deep purple dress with lilac lining along the bottom, center, top, and pockets, along with white spiked edging at the hem. She wears a white, short-jacket over this with a big N button, purple plug-like strings, and purple lining and buckles on each shoulder sleeve. Her choker remains the same, along with her socks and shoes. On her wrist she has white bracelets with a soft spiked material and small powder blue spots in the center.

Her new HDD form is largely similar to the previous version, with all traces of silver gone and far more blue. It sports no blocky patches and more pronounced purple and blue lines with a patch of purple material going from just below her breasts to just below her navel. The gamepad marks are moved from her shoulders to the sides of her hips. She also has two black and purple wristcuffs and more detailed stockings and boots. Neptune also gets an increase in bust size or bust emphasis.

Trivia
• Neptune is the only CPU who is based on a fictitious console (though the Sega Neptune, which was essentially a standalone version of the 32X addon for the Sega Genesis, was planned to be released, but ultimately cancelled upon the release of the Sega Saturn). Noire, Blanc and Vert are originally based on 7th generation consoles, while the last Sega home console is the 6th generation console Sega Dreamcast. Because it would be impossible for Planeptune to compete with the other nations if their CPU is based of an old console, a fictitious 7th generation Sega console had to be created. Since Hyperdimension Neptunia Victory, the other three CPUs represent all home consoles from all generations, while Neptune does not. Instead, the different versions of Planeptune from different dimensions have different CPUs based on real consoles from the past. However, Neptune's Next Form represents the fictitious 8th generation console of Sega to compete with the other Next Forms that are based on real 8th generation consoles.
• Neptune's personality in the localised version of the games and the original Japanese version of the games are quite different. While the localised version portrays her as silly and somewhat hip girl with a weird way of speaking, The Japanese version portrays her as somewhat spunkier girl who acts silly most of the time but can also be serious. It can be said that her personality in the localised version of the series is a highly exaggerated version of her original Japanese counterpart.
• Neptune's name is referred to as "Fictitious Hard" (Hard being short for Hardware) by the creators.
• The creator's favourite character in the series is Neptune, due to her being "energetic and bright to the point of idiocy". Even in the darkest situations, she still makes happy and positive comments.
The DLC costume Smile Spiral from Victory is a reference to the song called Smile Spiral that Neptune and Nepgear sing on the Hyperdimension Neptunia Duet Sisters Vol.1 CD. another thing to be noted is that the song Smile Spiral also appears in the Japanese idol DLC cutscene in the Japanese version of Victory, where Neptune and Nepgear sing Smile Spiral.
• In Victory, it is revealed Neptune doesn't like eggplants. The reason as to why is, according to Neptune, because they turn your eyes purple, even though Neptune's eyes are already purple. This strange phobia affects Neptune to the point that it can be used as a sort of kryptonite, and has been done so by Arfoire. However, if the eggplant is modified in some way so it no longer resembles an eggplant (like being extremely enlarged), Neptune won't be phased by it.
• Up until a certain part of Victory, Neptune didn't know what her HDD form looked like. This is mostly because said form is only used for battle and Neptune states she isn't the type to transform and just stare at mirror, saying Noire's more likely to do that. Though strangely enough, there is proof that Neptune knew what she looked like in HDD. The very beginning of the game has Neptune rewatching an old music video starring herself (and Nepgear) in HDD. But, it can easily be justified by saying that Neptune simply forgot, like she did with Arfoire earlier in the game, or she only pretended not to know as, when she saw a copy of HDD form, she proceeded to call the copy a very stylish and hip stranger.
• In the 2011 Neptunia popularity poll, Neptune ranked in second place. First went to Noire, a fact that was referenced and made fun of in Victory where Neptune, upon hearing of Noire's fandom, is immediately overcome with jealousy and begins calling Noire "Popular Heart" in a mocking way.
• In the 2014 Neptunia popularity poll, Neptune ranked in third place, behind Blanc, who was the winner, and IF, who ranked second place.
• In the first Hyperdimension Neptunia, when using Neptune Break, occasionally Neptune can be heard saying "up up down down left right" more than half of the "Konami Code" but then realising she has no use for it, and she stops.
• Out of the original four Goddesses, Neptune was the only one that didn't have a colour-themed name.
• In Victory, episode 7 of the anime, and Hyperdimension Neptunia Re;Birth 1, Neptune's favorite food is said to be custard pudding.
• In the first Hyperdimension Neptunia:
Neptune references one of Optimus Prime's Catch Phrases, when she says "Transform!" and "Roll out!"
• When Neptune enters a battle sometimes she will reference Sailor Moon, when she says "Pretty Mysterious Neptune of Love and Justice! In the name of the Basilicom, I'll punish you!"
• Unlike the other CPUs from the other three nations, Neptune's outfit does not have a regal theme, but has a very casual design. This trait is shared with the other two CPUs from the alternate Planeptunes.
• In the Hyperdevotion Noire Drama CD, Vert describes Purple Heart as a kuudere, despite she does not fit the stereotype by standard definition.
• During one of the Nepstation segments in chapter 7, Neptune and Uni make a Pretty Cure reference, with Neptune saying that "she totally loved it when Shiny Voluminous showed up". This is a reference to her Japanese voice actress's role as Shiny Luminous.
In the prologue of Re;Birth3, Neptune is able to mimic the voice and personality of her goddess form perfectly.
• The gun that the Ultra Dimension Neptune uses in combat is the same gun that Neptune uses for her ranged attacks in the original Hyperdimension Neptunia.
• In the official website of Megadimension Neptunia VII, it tells how the older Neptune seeks unusual insects. One part that shows that Older Neptune is the Neptune in the True Ending of Hyperdimension Neptunia Victory is that she caught Croire, whom she thought was a bug.
In both the Japanese and English dubs of Victory, her voice was higher-pitched, showing that she was a child at the time.
• In Victory, the CPUs joke that without the abilities of HDD, Neptune would've likely starved to death. When Nepgear and Uzume meet the older Neptune, she has actually run out of food.
• In Cyberdimension Neptunia: 4 Goddesses Online, Neptune mentions her shoe size is 22.5 cm, roughly the length of two game cartridges for the Sega 32X, one of the console components for the planned Sega Neptune.
• Despite being called pudgy due to her eating habits, out of the four Hearts she ties with Blanc in terms of weight, though she is taller than her.
• Neptune is the only goddess who has 2 limit break specials.
• Neptune shares her English Voice Actress (Melissa Fahn) with Tyria from Ar Tonelico III or Qoga in N/A, the violet-haired Origin Reyvateil whose personality is like a mix of Neptune's air-headed and carefree attitude with a deeper tone of voice that resembles that of Purple Heart's. She also strongly resembles Neptune's human and Goddess forms.
• One of Neptune's level-up quotes in mk2 is similar to the first few bars of the victory theme from the Final Fantasy game series.
• In Neptunia Victory, one of her facial expressions resembles the "Yukkuri" face, a Touhou meme of considerable infamy.
• The formation skills "Final Form CPU" is a tribute to Kamen Rider Decade's Final Form Ride, both similar that they change the others (in Neptune's case the other CPUs, and with Decade the other Kamen Riders) into weapons or objects they could use.
• In the Battle, Neptune is useful for Guard Breaks to be used in battle, Also, if her stats are increased, Her EXE DRIVE Becomes much stronger.
• Neptune's age is unknown, but just like the other CPUs she fought in the Console Wars, and even though it has no definitive beginning, the war went on for thousands of years, meaning she's several millennials old as a CPU Goddess entity.