The character known as Alvida is the captain of the Alvida Pirates and serves as the first pirate opponent encountered by Monkey D. Luffy at the very beginning of his journey. Initially a minor but memorable antagonist in the East Blue, Alvida undergoes a significant transformation that changes both her physical appearance and her role in the world.

Before her transformation, Alvida is a brutal and vain pirate captain. She is known by the epithet Iron Mace due to her immense weapon, a large, spiked iron club she wields with ease to crush anyone who displeases her. Her personality is tyrannical, short-tempered, and deeply narcissistic. She considers herself the most beautiful woman in the world, despite her original appearance being obese, unkempt, and covered in freckles. She forces her crew to affirm her beauty and violently punishes them for laziness or for failing to keep her ship, the Miss Love Duck, spotless. She holds the former cabin boy Koby as her prisoner, subjecting him to a life of fear and forced labor. Her modest bounty of five million berries reflects her status as a threat within the relatively peaceful East Blue, though her actual combat strength is low compared to later pirates. Luffy defeats her with a single punch after she insults him, a blow that also inadvertently sets Koby free.

A pivotal change occurs after her defeat. Alvida acquires and consumes the Sube Sube no Mi, a Paramecia-type Devil Fruit known as the Smooth-Smooth Fruit. This fruit has two major effects. The first is a dramatic physical transformation, shedding her former bulk and turning her into a tall, slender, and conventionally beautiful woman with smooth, flawless skin. The second effect is her primary combat ability: her skin becomes so frictionless that nearly all physical attacks and objects slide off her without causing harm. This power makes her incredibly difficult to injure directly, as swords glance off her and blunt force loses its impact. She can also use this slipperiness to reduce friction with the ground, allowing her to glide and slide at high speeds in a technique sometimes called the Sube Sube Spur.

Following her physical change, a notable shift in personality occurs. While still self-centered and proud of her new beauty, she becomes significantly more relaxed, cool-headed, and less prone to violent outbursts. Her voice becomes softer, and she adopts a more charming and confident demeanor, no longer needing to demand compliments as they come naturally from those around her. Despite this mellowing, she retains her practicality and self-preservation instinct, avoiding fights she cannot win and showing little patience for the chaotic antics of others.

Her motivations become tied to her encounter with Luffy. Ironically, the man who defeated her becomes an object of obsession, and she decides she wants to make him her man. To pursue him, she forms an alliance with another of Luffy's early enemies, Buggy the Clown, after saving him from drowning. This partnership marks the end of her independent crew, as her original subordinates disappear from the story. She becomes a co-captain in the Buggy and Alvida Alliance, later integrated into Buggy's Pirate Dispatch Organization, where she functions as one of its key executives. During Buggy's absence at the Impel Down prison and the Marineford War, she acts as the temporary captain of their combined forces, demonstrating a degree of leadership and loyalty to their mutual goal of tracking Luffy. Her key relationships are thus defined by her rivalry with and fixation on Luffy, her practical partnership with Buggy, and her former domination over Koby, who escaped her clutches to join the Marines. Her journey is one of transformation from a minor, ugly tyrant to a sleek, powerful, and recurring antagonist who finds a more stable place as a prominent member of a larger pirate organization.