Alicization is the 4th main Arc in the Sword Art Online series, spanning from June 26, 2026 and up to August so far, which corresponds to the light novel Volumes 009 to 018. It describes events related to Project Alicization 1/4, the Soul Translator (STL) gear, the simulated quantum souls Fluctlights, and the virtual world called Underworld where they live along with the real people who log in for various reasons.

Volume 015 begins the War of the Underworld sub-arc.

Story

Volume 009 - Alicization Beginning

Kirigaya Kazuto takes up a FullDive gear testing job from a company called Rath over three days with his memories of the experience blocked afterwards as a security measure. However, Rath is actually a Japanese Self Defense Force (JSDF) affiliate using Kirito's swordsmanship skills to improve their novel Fluctlight AI-developing VR, Underworld, whose clock is set at 5,000 times the real world's, where the residents somehow were too obedient for military use and needed a push. Kirito spends eleven years in Underworld's Rulid Village as a child and just another villager with no real-world memories until his and his friends' tasks result in a Taboo Index law infringement by Alice Zuberg who is arrested by an Integrity Knights (I.K.).

The experiment is over, and Kirito logs out, his memory blocked out for security reasons. Kazuto explains quantum mind (Fluctlight) theory to friends, then takes Asuna home. However, he is attacked halfway by Kanamoto "Johnny Black" Atsushi, a Death Gun member on the loose, and Kazuto's heart stops. He is kept alive but the severe lack of oxygen leaves him in a coma with major brain damage.

Kazuto wakes up in the VR world as six years have passed, his real-world memories intact. He meets Eugeo who does not remember him but clues him in about the world, and they go to save Alice's sister Selka from goblins, which then lets Eugeo complete his Sacred Task, or Calling, and strive to be a swordsman, and Eugeo and Kirito vaguely remember the old days now. They head out to save Alice.

Volume 010 - Alicization Running

Asuna and Yui trace Kazuto's position to a military sea base Ocean Turtle, and with Kōjiro Rinko's help Asuna infiltrates it and finds that the STL project faces Kikuoka Seijirō and Higa Takeru have kidnapped Kazuto and connected him to Underworld again to simulate his recovery via his Fluctlight.

Eugeo and Kirito go south from Rulid to Zakkaria town and work at a farm until they compete in the Norlangarth North Area Swordsmanship Competition. They win the tournament and get into the town's garrison, eventually earning the right to apply for the Sword Mastery Academy in Centoria to further become Integrity Knights so they can enter the Central Cathedral.

Volume 011 - Alicization Turning

Kirito and Eugo are second-years at the Academy, fifth and sixth-ranked among the twelve elite trainees. Their valets Ronye Arabel and Tiese Shtolienen ask them to help another valet being made to do embarrassing tasks. They break the Taboo Index, and Alice, an I.K. by now, takes them to the Axiom Church prison. The duo discover a way to break out, but I.K. Eldrie Synthesis Thirty-one (S31) interferes. They are rescued by a little girl calling herself Cardinal who tells them the real story of Quinella and the tyranny she has created.

Volume 012 - Alicization Running

Cardinal tells them more about Quinella becoming Administrator and how she makes new Integrity Knights, as well as how Cardinal System itself is now a little girl. She tells them of an eschatological future of the Dark Territory invasion. Kirito agrees to help defeat Quinella. Cardinal teaches him and Eugeo the Perfect Weapon Control Art. They return to the tower, near its Armory, and proceed to look for their weapons and reach the Cathedral top.

Volume 013 - Alicization Dividing

Asuna and Rinko notice the escort ship Nagato that unexpectedly changes course. Meanwhile, Kirito and Alice form a truce and trust each other's prowess. Eugeo fights his village's hero Bercouli whom Chudel, and Chudelkin kidnaps him. Kirito tells the truths he knows to Alice who wants to see the old Alice's family once. Eugeo meets the pontifex herself who tricks him into opening himself to Synthesis. He faces Kirito and Alice as an Integrity Knight.

Continued on page 2

References

• Alicization Arc - Fan Wiki
• Volumes 09 to 21 - Fan Wiki