It isn't unusual for creators to retroactively change how certain events played out or add details to explain how some aspects of their universe work. The famous Sword Art Online franchise is no different, with creator Reki Kawahara helping out with the anime adaptation to fill in some of the gaps.
Kawahara decided to go back and write a new take on the story's original "Aincrad" arc in the form of Sword Art Online: Progressive. After being asked to write a short story for director Tomohiko Ito to fill in some of the time gaps for Episode 2, Kawahara found that he liked being able to retroactively explain things. Here are a few of the biggest differences between the original Sword Art Online and its Progressive counterpart.
While both the original novels and the spin-off series focus on Kirito and Asuna trying to fight their way out of the deadly VR game they're trapped in, it isn't necessary to read Progressive to understand what's going on. It's more along the lines of supplemental material that looks to explain what the characters were doing during a two-year gap that was left out of the original novel, which only covered floors 1, 74 and 75 of the game's massive world.
The reason for the original Sword Art Online light novels not covering more was because it was being written for a contest and Kawahara needed to cut it down for length's sake. This led to certain events being glossed over and Asuna and Kirito's relationship not really being explored in depth. Some events that occurred on the other floors were told in smaller side-stories, but not all of the floors and their adventures were explained.
The Sword Art Online: Progressive novels seek to rectify this by exploring what happened on the other floors and how Kirito and Asuna's relationship developed. Each volume details what life is like on the different floors and within the game itself. Changes have been made along the way, one being the timeframe in which Asuna and Kirito begin to grow close. In the original series, they only came together a few months before escaping the game, but this is retconned to them bonding within a few months of knowing each other instead. Another change is that SAO was told mostly from Kirito's perspective, while Progressive is told through both his and Asuna's first-person views. Through Asuna's eyes, readers are able to see the flaws in Kirito that were only vaguely described before.
They meet on the first floor of Aincrad after Kirito saves Asuna from a horde of monsters she was underprepared for. After this, they partner up for the next boss raid because they don't know anyone else. Meanwhile, someone keeps trying to buy Kirito's weapon, to which he refuses each increased offer. During the raid, Kirito learns who was trying to buy his weapon and why, which prompts him to reveal himself as a beta tester and take on the hate everyone feels toward them. After entering the second floor, he and Asuna reconnect and expose a blacksmith scamming players out of their weapons.
Asuna and Kirito's story is told through alternating POVs while their in-game abilities and mods are also explained in more depth. They're able to use Kirito's knowledge from beta testing to complete quests that will help them reach the higher floors. The game's world and how it works is also explained in further detail, going into how concepts like "instances" work and why magic was cut out.
Kawahara has released eight volumes of Progressive so far, with seven translated into English. There has also been a manga adaptation that has Asuna take on the role of protagonist. An anime film adaptation was released in 2021 under the title of Sword Art Online the Movie -Progressive- Aria of a Starless Night with a second, Sword Art Online the Movie -Progressive- Scherzo of Deep Night, coming out later in 2022 that will cover the events of Aincrad's fifth floor.
