"Sword Art Online: Alicization Lycoris" is a manga adaptation of the "Alicization" arc from the "Sword Art Online" light novel series, focusing on Kirito’s journey into a virtual world with advanced artificial intelligence. The story begins with Kirito being recruited by Rath, a secretive organization, to test a new FullDive system called the Soul Translator. This system allows users to experience a virtual world at an accelerated time rate, simulating years within hours. Kirito is tasked with interacting with the inhabitants of the virtual realm, known as the Underworld, to observe their development.

Upon entering the Underworld, Kirito loses his memories and is found by a young boy named Eugeo. The two form a close bond and grow up together in the rural village of Rulid. Eugeo is burdened by a sacred task: to cut down a demon tree that has plagued the village for generations. Kirito, despite his amnesia, retains his combat skills and helps Eugeo achieve this goal. The two then leave their village to attend the Swordcraft Academy in the capital, where they train to become Integrity Knights, elite warriors who serve the Axiom Church.

As Kirito and Eugeo progress through their training, they uncover unsettling truths about the Axiom Church and its ruler, Administrator. The Church enforces strict laws to maintain control over the Underworld, suppressing free will and punishing dissent. Kirito’s memories gradually return, revealing his mission and the true nature of the Underworld as a testing ground for artificial fluctlights—human-like AI capable of genuine emotions and growth. The stakes escalate as Kirito and Eugeo confront the Church’s oppressive regime, leading to intense battles and moral dilemmas.

Key characters include Kirito, the skilled swordsman and protagonist; Eugeo, his loyal and determined friend; Alice Zuberg, a childhood friend of Eugeo who becomes an Integrity Knight; and Administrator, the enigmatic ruler of the Axiom Church. The narrative explores themes of artificial intelligence, free will, and the ethical implications of creating sentient beings. The story builds toward a climactic conflict as Kirito and his allies challenge the Church’s authority, striving to protect the Underworld and its inhabitants from exploitation and destruction.