Nefertari Vivi is the princess of the desert kingdom of Alabasta and the daughter of King Nefertari Cobra and Queen Titi. As a member of the Nefertari family, she carries the initial D. in her name, a detail tied to the deeper mysteries of the world. During her childhood, she belonged to the Suna Suna Clan, where she served as the vice-leader of a group led by her friend Koza, an experience that gave her an early understanding of the lives and concerns of ordinary people.

Vivi is introduced under the alias Miss Wednesday, a bounty hunter and agent of the criminal organization Baroque Works. In truth, she had infiltrated the organization to uncover the identity of its leader, who was revealed to be Sir Crocodile, one of the Seven Warlords of the Sea. Crocodile had been using manufactured drought, propaganda, and hidden schemes to destabilize Alabasta and seize control of the kingdom. Vivi's mission was to gather intelligence from within and find a way to save her homeland from ruin.

Her personality is defined by an unwavering sense of responsibility and deep compassion for others. As heir to the throne, she places the welfare of her kingdom above her own desires, even when doing so requires painful personal sacrifice. She does not seek glory or power; her goal is to protect those who cannot protect themselves. Her courage takes the form of quiet, persistent determination rather than reckless bravado, and she is known for her willingness to risk her own safety to help others, even without expecting anything in return. Despite her royal upbringing, she is approachable, warm, and empathetic, crying easily when moved and laughing freely with friends. She can show a sharp temper when provoked, particularly when her kingdom or her companions are threatened, but she generally keeps her emotions disciplined through the habits of diplomacy. Her ability to inspire loyalty comes from genuine care rather than authority, making her a natural leader whose people follow her out of trust in her vision of peace.

Her central motivation is to protect Alabasta and its people from the war and chaos engineered by Crocodile. She is driven by the example of her father, who ruled through accountability and by listening to his subjects, and she sees the conspiracy against her kingdom as an attack on the social contract her family has maintained for generations. She is also motivated by a desire to reveal the truth to her people and to prevent a civil war that could destroy the nation.

In the story, Vivi is a central figure of the Alabasta saga. After her cover begins to crumble, she seeks help from the Straw Hat Pirates, and the crew chooses to support her. She travels with them from Whiskey Peak through Little Garden and Drum Island before reaching Alabasta, where their alliance is essential to exposing Crocodile's plans and stopping the civil war. At the end of the conflict, Vivi considers joining the crew permanently but decides to remain in her kingdom to fulfill her duties as princess. The Straw Hats honor her choice while making clear that she will always be considered one of them, symbolized by the X mark they drew on their arms as a sign of their bond. She is regarded as an honorary member of the crew and remains connected to them even after returning home. In later events, during the Reverie, her father King Cobra is killed and Vivi herself becomes a target of the World Government, forcing her to go into hiding while carrying forward her family's connection to the ancient history of the Void Century and the Poneglyphs.

Her key relationships include her father, King Cobra, whose leadership style shaped her own values; her childhood friend Koza, who became a leader of the rebel forces and a central figure in the conflict; and Karoo, her loyal Super Spot-Billed Duck companion who serves as her steed and partner. Among the Straw Hats, she forms a particularly close friendship with Nami, and she shares a deep mutual respect with the rest of the crew, including Luffy. She is also known for nicknaming Zoro Mr. Bushido. Her bond with the Straw Hats endures despite the physical distance between them.

Vivi undergoes significant development over the course of her journey. She begins as a disguised agent trying to work within the system, but her experiences reshape her understanding of leadership and conviction. Watching the giants Dorry and Brogy, whose century-long duel is based on honor rather than hatred, teaches her to respect beliefs that run deeper than logic. Witnessing the tyranny of King Wapol on Drum Island gives her a clear example of what happens when leadership fails completely. Her defining moment comes in Alabasta, when she stands on a clock tower and cries out to her people, begging them to stop fighting one another. That plea reflects her growth from a fugitive seeking information into a leader willing to face her nation openly and appeal to their better nature. Over time, she matures into a courageous leader capable of sacrificing everything for the safety of her people.

Vivi has no Devil Fruit powers. She is a skilled combatant who relies on a unique weapon called the Peacock Slasher, consisting of two metal rings connected by a sharp wire. Her fighting style, known as the Peacock Dance, uses fluid and acrobatic movements that make her a difficult target while allowing her to strike from unexpected angles. She possesses strong physical conditioning, agility, and resilience developed through years of undercover work and travel on the Grand Line. Her true strengths, however, lie in her strategic mind, her ability to plan complex operations, and her skill at reading the motives of others, sharpened by her time as a spy. She also possesses a distinctive ability passed down through the Nefertari royal family: mastery of the Super Spot-Billed Duck Whistle, a communication technique that allows her to summon and command Karoo and other ducks of Alabasta. In addition, she has significant diplomatic and political skills honed through her royal training, which enable her to navigate the affairs of the World Government, negotiate with other leaders, and inspire trust among her subjects.