OVA
Description
Neptune functions as the CPU of Planeptune, embodying a fictional Sega console based on the unreleased Sega Neptune. Banished to Gamindustri following a celestial conflict, she suffered memory loss and later gathered allies to defeat the goddess Arfoire. She consistently maintains the role of older sister to Nepgear across all continuities.

Her human form displays a carefree, impulsive, and klutzy personality, frequently expressing affection through physical contact and nicknames. She exhibits strong protectiveness towards Nepgear and regularly teases fellow CPU Noire. A notable love for food, especially pudding, contrasts sharply with an intense aversion to eggplants. This form stands 146 cm tall, featuring purple eyes and purple shoulder-length hair secured by gamepad-shaped clips, typically dressed in a white hooded dress with purple accents.

Transformation into Purple Heart (HDD form) triggers significant physical and personality shifts. Height increases to 164 cm, hair transforms into dark purple twin-tail braids reaching nearly her feet, and eyes turn blue. The combat suit evolves across appearances but consistently incorporates a black bodysuit with purple and blue armor elements. Her personality shifts toward seriousness, strategic observation, and confidence, though later media shows traces of Neptune's original playfulness. Voice modulation deepens noticeably. This form wields broadswords, demonstrates flight via glyphs, utilizes healing magic, and employs EXE Drive techniques like "Dimensional Slice" alongside jet transformation for missile attacks.

In "Nep-Nep Darake no Festival", Neptune exhausts herself preparing for Planeptune's Costume Festival, leading to transportation to a dream island for lethargic goddesses. There, she confronts "Neptune GT", a manifestation of her own laziness, while her interdimensional counterpart assists Nepgear with festival events by wearing a Generator Unit costume. The storyline reinforces her struggle between work ethic and procrastination, culminating in renewed dedication after reconciling with her lazy counterpart.

Character development across media shows progression from early irresponsibility toward protective leadership, particularly evident in protecting Nepgear during capture events in "mk2" and dimensional travels in "Victory". Relationships with fellow CPUs evolve from initial rivalry to cooperation, though she consistently targets Noire for teasing. Persistent traits include fourth-wall awareness and self-referential protagonist remarks.

Dimensional variants appear, including an Ultra Dimension counterpart referenced later and the "Older Neptune" seen in the festival OVA. Hardware specifications describe her fictional console with conversational AI, multi-core processing, and purple-ray disc capabilities, details remaining peripheral to narrative roles.