The following contains spoilers for the Sword Art Online light novel series.
Though the anime still has a ways to go, one of the first iterations of Sword Art Online is slowly drawing to a close. The light novels are now in their seemingly final arc, with the "Unital Ring" storyline being the series' curtain call. To this end, it's bringing back characters from the story's beginning, including an information broker who hasn't been seen in a long time.
Though she wasn't a main character, Argo the Rat was a vital part of the "Aincrad" storyline in the beginning of Sword Art Online. She hasn't had much of a role since then, but she's finally back in the novels' curtain call. While this might seem random, the full-circle effect speaks volumes in terms of the creator's intentions for the series. Here's a look at Argo's role in Sword Art Online and why her return is so important.
Argo the Rat Debuted in Sword Art Online's First Storyline
Like main characters Kirito and his friend/love interest Asuna, Argo made her debut in the initial "Aincraid" arc of Sword Art Online. One of the 10,000 players who found themselves stuck in the game, Argo (whose real name is Hosaka Carina Tomo) was also a beta tester who strangely enough didn't use this completely for her own goals. Becoming a businesswoman, Argo sold information and secrets concerning the game through guides. Even though she sold these clues and tips for a price, she was likely an invaluable part of many players staying alive for as long as they did. Even Kirito used her services and aid, with the beta tester offering them to him freely.
It's interesting that she managed to initially survive in the world of Aincrad for so long, as she had otherwise determined that she wasn't fit for combat and adventuring. Of course, once Kirito defeated Heathcliff, Argo and the other surviving players were freed from their video game prison. Her role was expanded upon in the Sword Art Online: Progressive movies and novels, which were a retelling of the "Aincrad" arc with a greater focus on the surrounding world. This is where her prominence in the animated form of the franchise came from, with the anime series itself only referencing her. Progressive made her more than just a plot device, with the novels even showing her gaining martial arts skills. The movie versions of Progressive have acted as her biggest rise to fame, but the newest chapters in the light novel could change that once they're adapted into anime form.
Argo the Rat's Return Sets the Stage for the End of Sword Art Online
Following the events of the "Aincraid" arc of Sword Art Online, Argo/Tomo resumed her normal life and went to high school. She even became a writer for an MMO magazine, with her experience during the Aincrad incident making her perfect for such a task. She also joined a school for survivors of Sword Art Online, showing how the traumatic events of the game were actually somewhat beneficial. Beyond the expanded events of the Progressive series, she hadn't been much of a presence in the series. That's now changed with "Unital Ring," which is in many ways different from previous arcs.
"Unital Ring" isn't based on a previous Sword Art Online story arc from the original web novels. Instead, the light novel arc is entirely new, and it's supposed to be the final part of the main series' storyline. In bringing things to a close, it's also bringing back characters who were there when everything started. So far in the light novels, Argo/Tomo has seen a bit more character development and is out of her usual element. This begins with her meeting Kirito at his school, bringing the story full circle by having her then become vital to the ensuing "Unital Ring" plot. Ironically, many fans had hypothesized that she died off-screen at some point. That's not the case, but the return of a character from the initial arc signals that this truly is the beginning of the end for Sword Art Online.