Episode 2 of Sword Art Online: Alicization , titled "The Demon Tree," serves as the foundational "world-building" chapter for the Underworld arc. Picking up immediately after Kirito is attacked in the real world by Johnny Black, the episode shifts from the high-stakes tension of the series premiere to a slow-burn introduction of the new virtual reality.

A primary theme of the episode is the blur between reality and simulation.

While exploring, Kirito finds a boy named Eugeo tasked with chopping down a massive tree known as the Gigas Cedar or "The Demon Tree".

Because Kirito cannot explain his origin or "Calling," Eugeo identifies him as a "lost child of Vecta," a legendary figure spirited away by the dark God Vecta.