- Not to be confused with Neptune/VS Sega Hard Girls
The Neptune whose soul is trapped in the Nepbike, which was originally IF's green motorbike. She adopts the original bike's ability to travel through time and accompanies IF and Hatsumi Sega on their mission to save history.
The Nepbike is her current form she is forever trapped in. Due to mysterious circumstances, her soul has possessed IF's motorbike, causing its color to change from green to "eggplant-colored". Despite being a bike, Neptune is able to talk in this form and can express her emotions through her voice without any limitation. However, she is unable to move by her own and she can be caught in a helpless situation where she is unable to defend herself from other people, e.g. Nepgear who tries to dismantle her. Neptune has inherited the abilty to travel through time from IF's original bike, allowing her and other characters to travel through different timelines. Her demeanor has not changed from her human form.
Even after being trapped inside a motorcycle, Neptune's personality is the same as her human personality and she adapts to her situation very quickly.
Neptune is the human form of the CPU Purple Heart. She is often considered to be energetic and dorky. Her favorite food is custard pudding and she loves playing video games. While she enjoys playing all games, she especially loves Retro video games. Since she is trapped in her Nepbike form, Neptune never returns to her human self.
Neptune had short lilac hair with bangs that reach down to her collar bone and purple eyes. In her hair she wore white hair-clips in the shape of D-pads and around her neck is a choker that has a light blue D-pad symbol on it. She wore a mostly white hoodie dress that had a light purple hood, strings that looked like controller plugs, and two huge purple and white pockets with purple D-Pad symbols on them. The sleeves had two light blue strips going all the way down while the front of the hoodie only contains one. The ends of the sleeves and the bottom of the hoodie had dark and light purple stripes. The zipper emblem and the back of the hoodie had a purple letter "N" to represent the first symbol of her name. She wore light blue and white striped thigh high socks with frills at the tops and her shoes are purple and blue.
She is a happy, excitable girl with a very strong sense of justice. Her ditzy personality causes her to be very careless at times which can either help her or land her into serious trouble. She makes friends rather easily due to her friendly nature and often gives them cute nicknames. People admire her optimistic outlook and confidence. She never gives up or backs down when the going gets tough and she makes sure to see her objective through to the very end. Neptune does not like fighting and is rather pacifistic, prefering to avoid conflicts whenever possible. But when she has to fight, she can act seriously.
Purple Heart is the goddess form of Neptune. She is considered to be cool, collected, just, and overall much more mature in comparison to her human form. While the personality and appearance change is major between the two forms, she still retains some aspects of her human form albeit to a lesser extent. Since she is trapped in her Nepbike form, Neptune never returns to her goddess self.
Purple Heart's appearance in her Lost Purple Core was reminiscent of the Purple Core but with much more stylization and design. Her hair and hair clips remained the same while her bodysuit, while still black, had purple and blue lining all around the torso and arms. The middle of the torso has purple mesh, allowing a vague vertical view of her stomach. She also wore thigh high boots with octagon patterns on the side at the very top; one filled it with purple and another just a white outline.
Purple Heart was a serious and mature person. She's often calm and rarely changes facial expressions. She was a very observant and intelligent female, thinking in a rational matter most of the time. She was the complete opposite of her human form in many aspects, but her strong sense of justice and confidence remained unchanged. It can be said that Purple Heart was a bit arrogant, having a strong confidence in her abilities and believing that no one can defeat her. She could keep convincing poker faces, as shown during her duel with Sega Saturn. Despite her rivalry with Saturn, she was very concerned for Saturn's health and desperately tried to save her, only to be deeply saddened by her death. Even though she just knew them for a short time, Purple Heart sacrificed her life for IF and Segami and trusted them that they could save history.
Seemingly all of Purple Heart's personality traits have been gone after Neptune ended up possessing IF's motorbike, since Neptune has retained only her human personality so far.
When history was erasing, Neptune/Purple Heart saved IF and Hatsumi Sega at the cost of her own life, but she ended up possessing IF's bike.
- During dialogue cutscenes, Neptune in her bike form is unable to show emotions through facial expressions. However, in the last story CG, a smiley can be seen on Neptune's windshield.
- There are three CGs that depict Neptune being confronted by Sega Saturn in public and Purple Heart witnessing Saturn's demise. The Neptune in the first CG is both this Neptune and the other Neptune, while the Purple Heart in the second and third CG is only this Neptune.
- It is unknown how this Neptune is still able to exist, as due to how IF and Segami saved Neptune, the Nepbike would not have been able to be made. It is possible that a new timeline was created.
- Neptune's bike form has some resemblance to a 1998 Honda VFR