Carli Carmine is a character who begins her journey as an aspiring and somewhat hapless news reporter, driven by a deep-seated desire to document the success and struggles of others. Her background is marked by a persistent lack of professional success; she is clumsy, easily distracted, and often finds her efforts thwarted by bad luck or external circumstances. In some depictions, she is described as an unpaid intern who maintains a blog about street duels, always chasing a major scoop that seems to elude her. This constant striving, however, is balanced by a genuinely kind heart and an optimistic determination not to return to the difficult circumstances she may have faced in the past.

Carli's most defining trait is her earnest, almost fangirlish, admiration for the duelist Jack Atlas. After a chance encounter where she helps him during a vulnerable moment, this admiration deepens into genuine affection. She is willing to go to great lengths to support him, even disguising herself as a nurse to help him escape the hospital. Her initial personality is that of a bubbly and caring individual, but she also displays a selfish streak in her desire to keep Jack close, a trait that ultimately contributes to her tragic downfall. Driven by a need to uncover the truth about the Signers and to stay connected to Jack, she investigates the mysterious Arcadia Movement. This quest leads to her being discovered, challenged to a duel, and thrown from a high window to her death.

Her death, however, is not the end. Overwhelmed by her feelings for Jack and her despair at being separated from him, she is resurrected as a Dark Signer, marked by the hummingbird symbol. In this new form, her personality shifts to a darker, more vengeful, and arrogant version of herself, though it is implied this is heavily influenced by the malevolent power of her Earthbound Immortal. As a Dark Signer, her primary motivation becomes to claim Jack for herself, believing that by defeating him and transforming him into a Dark Signer, they can rule a chaotic new world together. She engages Jack in a fateful Turbo Duel, using her power to trap him in an illusory future where he succumbs to darkness. However, Jack's belief in her true nature helps her break free from the dark influence. She ultimately sacrifices herself to prevent her own trap from destroying him, returning to her righteous self as she fades away in his arms. Following the final defeat of the Dark Signers, she is resurrected again, returning to her normal life, though her memories of her time as a Dark Signer are erased. In later storylines, her role shifts to a more comedic one, often appearing as a member of Jack's unofficial fan club.

The central relationship in her life is with Jack Atlas. She begins as his self-proclaimed number one fan, becomes a close confidant who helps restore his confidence, and later serves as his tragic adversary. Their bond is unique, as she is one of the few characters who truly understands his past. This relationship creates rivalries with other women close to Jack, such as his assistant Mina. Before her death, she also has key interactions with the psychic duelist Sayer, who murders her, and the model Misty Tredwell, who becomes a fellow Dark Signer.

As a duelist, Carli uses two distinct decks. In her normal life, she uses a Fortune Fairy deck, which is themed around fortune-telling and luck. After becoming a Dark Signer, these cards evolve into the more powerful Fortune Lady archetype. These monsters, each representing a different attribute, grow stronger as their levels increase, allowing her to control the field and deal effect damage. Her most notable ability and signature card as a Dark Signer is her Earthbound Immortal, Aslla Piscu, a massive hummingbird-like creature. As a Dark Signer, she also demonstrates the ability to create realistic, dream-like illusions, a power she uses to show Jack a vision of a dark future. Her skills extend to piloting a Duel Runner, which she handles with great proficiency after her transformation.