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Underworld (アンダーワールド, Andāwārudo?) is a one-hour-long first episode of the Sword Art Online Alicization anime adaptation. It aired on October 6, 2018.


Kirito checking the Gigas Cedar's Durability

On the 18th Day of the 7th Month of the Human Empire Calendar, Eugeo and Kirito, two eleven year-old children living in a village closest to the northern edge of the Human Empire, were hard at work at their Sacred Task. Their lifelong daily task was to cut the Gigas Cedar, a gigantic tree that prevented the growth of their village. Despite receiving their task a year and three months before, the two boys barely managed to leave a dent in the gigantic tree's Durability each day, just as the six generations of carvers before them.

Alice scolding Eugeo and Kirito for dawdling

Dejected by the lack of progress made, Kirito started a tickling fight against Eugeo, as his partner did not share his concerns about their task being uncompletable. The tickling fight was interrupted by their childhood friend Alice Zuberg, who came to bring them their daily lunch after finishing her studies. However, due to the heat and the long trip from the village to the tree, the two boys had to hastily eat the food before it spoiled. Concerned by this, Kirito recalled a cave mentioned in the «Bercouli and the Northern White Dragon» legend and proposed to travel to the cave to acquire some ice.

Alice, Eugeo and Kirito finding the skeleton of the Northern White Dragon, and its treasure

On their next rest day three days later, the three children travelled to the Northern Cave. There, they discovered that the dragon from the legend had already been killed, while its treasure, including the Blue Rose Sword, remained. However, feeling that taking any of the treasure would be akin to grave robbing, the children decided to only take some ice as planned. Just as they finished packing the ice and were about to head home, the trio realised that there was more than one exit from the room and they had lost track of which passage they had used themselves.

The Integrity Knight and Dark Knight locking swords

Following Alice's directions, the three children chose the closest passage for their return trip. At the end of the passage, however, the trio discovered that they had mistakenly chosen a path that led to the Dark Territory, the land of darkness outside the Human Empire where various demi-humans lived. At that moment, the three of them noticed a battle taking place between an Integrity Knight, a guardian of the Human Empire, and a knight from the Dark Territory, both riding dragons in mid-air. The Integrity Knight dispatched the dark knight moments later, causing the latter to crash close to the entrance to the cave.

Alice breaking the Taboo Index by touching the ground of Dark Territory

As the dark knight attempted to reach out to the children for help, Alice subconsciously began approaching the knight; however, the girl tripped the moment Kirito warned her to stop, resulting in her fingertips accidentally touching the ground of the Dark Territory and thus breaching a clause of the Taboo Index, the ultimate law of the Human Empire. To their surprise, a head appeared behind the children the next moment, logging Alice's identity and actions in a language the trio did not understand, before disappearing. Confused by what had taken place, the children decided to return to the village.

Eugeo and Kirito powerlessly watching as Alice is taken by the Integrity Knight

The following day, the Integrity Knight they had encountered in the Dark Territory, Deusolbert Synthesis Seven, arrived at the village to arrest Alice for her crimes, claiming that she would be executed after an interrogation. Shocked by this declaration, Kirito attempted to attack the knight to provide Eugeo with the chance to rescue Alice; however, the boy was assailed by a wave of energy, causing him to be brought to the ground, just before the other villagers to restrained him. When Eugeo attempted to come to Alice's aid himself, he was assailed by a pain in his right eye, halting his actions as Alice was flown away by the knight and his dragon. Some time later, Kirigaya Kazuto (Kirito) awoke from his FullDive.

Sinon asking Asuna to meet with her in the real world

On June 27, 2026, per Sinon's request, Asuna, Kirito, Klein, Lisbeth, and Silica came to Gun Gale Online to assist the sniper in a battle against a strange group of player killers in the game that had recently been massacring isolated squadrons in the fields. However, the commander of the player killers ordered his men to retreat midway through the battle, deciding that the battle against an irregular squad would not benefit their training for an upcoming operation. In the aftermath of the battle, Sinon met with her teammates at a bar to discuss the battle. When everyone began logging out, Sinon requested that Asuna and Kirito meet her in the real world the following day, thus Asuna proposed having their meeting at the Dicey Cafe, before leaving the game.

Kazuto surprised by Asuna's arrival

On June 28, 2026, Asada Shino (Sinon) and Kirigaya Kazuto came to the cafe, where the two began talking about the recent Bullet of Bullets IV tournament, where Shino had lost to an infamous player named Subtilizer. Believing that the man was able to predict the actions of veterans, Shino invited Kazuto to join her in the following Bullet of Bullets tournament at the end of the year, with the hopes that his irregular fighting style would allow them to defeat the champion. Just as the two finished covering a side topic about Shinkawa Kyouji's state, the Death Gun incident, and the last remaining member of the murderer group yet to be apprehended, Asuna arrived at the cafe, revealing that Shino had also asked her to help with the upcoming Bullet of Bullets tournament.

Asuna checking Kazuto's vitals through an app on her phone

Moments after agreeing to help Shino with the tournament, Asuna noticed that Kazuto had seemingly lost weight and complained that this was likely the result of his new part-time job, before checking on his condition through an app on her phone that received real time data from a sensor implanted into Kazuto's chest as part of his work. As the suspicious nature of his job aroused Shino's curiosity, Kazuto explained that he had been testing a new FullDive system, developed by a company named Rath, that was fundamentally different from other FullDive consoles.

Kazuto explaining the concepts of Fluctlights and the Soul Translator to Asuna and Shino

This machine, known as a Soul Translator, functioned by interacting with the user's Fluctlight — the equivalent of a human soul — rather than the brain. Using this, the device could write short-term memories onto the Fluctlight to convey sensory information, allowing it to create a virtual world akin to a realistic dream, as well as allowing the user to experience a subjectively longer Dive than it actually lasted. Although Kazuto was unable to recall his last Dive that lasted three days in real world time, as Rath had restricted his memories for confidentiality reasons, he did learn that the experimental virtual world was codenamed as Underworld.

Asuna and Kazuto's kiss after their talk about going to America together

After finishing their conversation and leaving the cafe, Kazuto decided to accompany Asuna home. Along the way, Kazuto shared his decision to leave to America, where research on the next generation FullDive technology was more advanced than in Japan, as he desired to see where the technology would lead to. However, unable to imagine his future without Asuna, the boy expressed his hope that the girl would accompany him on his journey. Overjoyed when she gladly accepted his request, Kazuto shared a kiss with his beloved partner. Moments later, when Asuna enquired why he lacked interest in the Soul Translator technology, Kazuto admitted feeling that it was an extension of Kayaba Akihiko's philosophy, thus he did not want to feel as if Akihiko was manipulating his future by choosing to participate in the Soul Translator research.

Atsushi and Kazuto's scuffle

At that moment, the pair's conversation on the Soul Translator was interrupted by a man asking for directions to the station. Just as Asuna was about to help the man, Kazuto revealed noticing that the man had been stalking them all the way from the Dicey Cafe. This prompted the man to abandon his act, declaring to be a member of Laughing Coffin and providing hints that allowed Kazuto to recognise him as Johnny Black (Kanamoto Atsushi). When Atsushi drew a vial of succinylcholine, a muscle relaxant, as he charged at the boy, Kazuto realised that he was facing the final member of the Death Gun trio, who had yet to be apprehended. Pushing Asuna away to safety, Kazuto attempted to counterattack with his umbrella; however, he was injected with the drug during the scuffle just as his umbrella pierced the man's leg, causing the boy to collapse due to cardiac arrest.

New Characters[]


  • Underworld
  • Real World
    • Rath's Roppongi branch base
  • Gun Gale Online
    • Field
    • Bar
  • Real World
    • Dicey Cafe

Adaptation Notes[]

Adapted from Volume 9, Prologue I - Interlude I
  • Eugeo's complaint about Kirito's frequency of checking the Durability of the Gigas Cedar was omitted.
  • The fact that the lunch brought to Eugeo and Kirito by Alice was sometimes made with the help of her mother, Sadina, was omitted from the anime. However, the anime did show the knowing smile the two kids shared when they realized that it was was one of those days Alice had help with making the lunch.
  • The children considering other options to cool their lunch was omitted from the anime.
  • The visualization of the «Bercouli and the Northern White Dragon» myth did not include the part where blue roses grew around Bercouli's feet, causing him to collapse, and awake the dragon. Instead, the dragon was shown to awake just as Bercouli grabbed the sword.
  • The scene where Eugeo and Kirito waited for Alice in Rulid on the morning of the cave visit was omitted.
  • In the novel, instead of talking about Alice and her future, the two boys discussed the possibility of becoming knights if they could manage to finish their current Sacred Task.
  • While en route to the cave, Eugeo was supposed to check whether the river was cold.
  • The System Call for generating a light source was changed from "Lit Small Rod" into "Generate Luminous Element. Adhere."
  • The scene of Eugeo and Kirito asking a farmer for directions as to where the Integrity Knight on the dragon went, since it was no longer visible to them during their chase, was omitted from the anime.
  • The scene were Deusolbert Synthesis Seven appeared to apprehend Alice, omitted various events:
    • Gasupht did not ask to hear the story from Alice's side.
    • Kirito and Eugeo did not preemptively try to help Alice run away.
    • Deusolbert did not command the villagers to bring Alice to him.
  • In the novel, Alice was bound after Kirito pleaded the knight for mercy. Meanwhile, the two boys were pulled back and forced to their knees.
  • In the novel, Eugeo and Kirito were being dragged out of the square under the village chief's orders when Kirito attempted to attack the knight.
  • The scene of Kazuto awaking from the Soul Translator was anime-original.
  • The scenes inside GGO were anime-original. The scenes also featured cameos of Fatal Bullet characters: Kureha and Zeliska could be seen playing pool at the bar; Itsuki's and Kureha's names appeared on the 4th Bullet of Bullets rankings, placed at 5th and 10th place respectively.
  • In the novel, Shinkawa Kyouji was one of the first topics Kazuto and Shino discussed. Additionally, the anime did not mention any of the details on Kyouji's fate or his state.
  • The discussion regarding Kyouji was followed by Shino talking about Shino watching old gun-related action movies that she had borrowed from Kirito.
  • The anime omitted the scene of Kazuto ordering baked beans, as well as Andrew mischievously bringing an extra serving for Shino out of Kazuto's tab.
  • Details of Sinon's encounter with Subtilizer, as well as the latter's playstyle, during the 4th Bullet of Bullets were omitted.
  • In the novel, Kazuto became aware that Asuna would be coming to the cafe before the girl had actually arrived, as Shino's hints prompted him to check his phone, which indicated Asuna's position.
  • References to Ordinal Scale were made in the Dicey Cafe scene in the anime, including mentioning the Augma, as well as showing the promise ring Kazuto had given to Asuna in Ordinal Scale.
  • The conversation about the Soul Translator and its mechanics was shortened for the anime adaptation.
  • Kazuto did not mention the the room full of cats that he experienced during one of his first STL tests, where his memories were not yet restricted.
  • While Kazuto's caution upon leaving the Dicey cafe was showcased, Shino's uneasiness was omitted.
  • In the light novels, it was Kazuto who initiated the discussion about going to America. In the anime, it was Asuna who started it after Kazuto came to a stop.
  • During the assault by Kanamoto Atsushi, Asuna did not go to nearby houses to ask for help.


  • In the scene where Sinon asked Asuna to meet her in real life, the logo of Fatal Bullet was shown on a building in Gun Gale Online, as a promotion for the game.



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