AL is the AI system that came built into the ARX-7 Arbalest. Once Sousuke first piloted the mecha during a hijacking incident, AL locked onto him permanently—and since the original programmer is dead, there's no way to reprogram it for anyone else.
Early on, AL was just a standard arm slave operating system, but it gradually developed a genuine personality as the series went on. It started picking up AM/FM radio stations to expand its vocabulary and understanding of human culture, which led to it doing things like cracking jokes, pointing out Sousuke's flaws, and making random quips in the middle of combat. Sousuke, naturally, wasn't thrilled about any of this.
Things got messy during the "End of Day by Day" novels. The tension between them was so bad that the Arbalest's Lambda Driver became almost completely useless, and Sousuke got frustrated enough to ask for a regular M9 instead. Eventually they worked through it though, and by the end they'd developed genuine mutual respect—enough to get the Lambda Driver operating at unprecedented levels.
By "A Dancing Very Merry Christmas" and "Continuing On My Own," AL had analyzed nine months of combat data and taught itself to pull off autonomous advanced maneuvers and precision shots with the Arbalest's weapons. That all changed when the Arbalest got destroyed at the end of "Continuing On My Own"—Wraith recovered both AL and the Lambda Driver from the wreckage.
"Burning One Man Force" reveals that Wraith brought AL to a surviving Mithril base in Anchorage, Alaska. There, AL worked with Sarah Miller to build an entirely new arm slave designed specifically around Sousuke's combat style: the ARX-8 Laevatein, named after a legendary Norse sword.
By "Come Make My Day," AL and Sousuke have both admitted they missed each other. AL's personality has matured enough to mirror what Sousuke might've been like if he'd had a different upbringing—though it still hasn't toned down the weird jokes and offbeat humor that defines the whole Full Metal Panic! vibe.
Content compiled by AnimeList.moe from publicly available sources.
