Carly Nagisa is a reporter who came from the country to seek out her dreams. She tends to get pushed around by others as she attempts to obtain a big scoop and is generally called "Stutter Stammer Carly" due to her nervousness. She carries around a Fortune Telling Deck which she uses to predict her fortune and give her tips for the day. Sometimes having to live in her car, Carly uses a Duel Disk radar that is able to detect the location of duels occurring nearby, which she used to locate Yusei Fudo during his duel with Dick Pitt. From then on she tries to investigate Yusei's "glowing arm", which leads her into learning about the Signers, Dark Signers, and even the Zero Reverse incident. But all throughout her investigations she encounters obstacles that prevent her from leaving the scene with the scoop she needs. She also develops feelings for Jack Atlus after she assists in his recovery after his duel with Yusei in the Fortune Cup.
Later in the story,
Carly is investigating the Arcadia Movement for information regarding the Signers when Divine catches her. Divine challenges her to a Psychic Duel, which ends in Carly plummeting from the high skyscraper level to the ground below, where she dies on impact. She is then immediately revived as a Dark Signer with the Hummingbird mark and she duels Divine in a Yami no Duel for revenge. The duel ends with Carly summoning her Earthbound God and sending Divine to face the same death she did. But after the duel, Carly returns to her normal self and is left confused and scared about her change to a Dark Signer and about the actions she committed.
However, her Dark Signer state returns in her duel with Jack and she manages to put a major dent in Jack's life points. Then, she tries to convince Jack to join the Dark Signers by using "the card that showed her Fate." However, her plan fails and Jack continues to battle her. Jack then later reveals during the duel that he had developed feelings for her and he tries everything in his power to save her. However, he defeats her, but she still turns to dust in the end. Before she does, she told Jack that she loved him.
Her Dark Signer deck is an evolved version of her previous Fortune Telling deck, where her cute "Fortune Telling Witches" have grown up into more intimidating (and evil) "Fortune Ladies". She uses a Field Spell, Fortune Vision, to send hers and her opponent's monsters into the future, a strategy that is beneficial to her while detrimental to her opponent.
However, when all the former Dark Signers return after the final Dark Signer battle, Carly has no recollection of her days as a Dark Signer. She is seen as the bumbling reporter who follows Jack everywhere. She is present when Jack battles Ghost, who looks like him. She is also present in Jack's battle against Andore in the WRGP and in the hospital where Jack is placed after he took a dangerous fall from his D-Wheel in defeat after the duel.