Canon film that introduces technology and characters relevant to Alicization .
The "War of Underworld" sub-arc is divided into two main parts: Sword Art Online: Alicization - War of Underworld
Episodes 25–47 (often split into Part 1 and Part 2). Plot Arcs & Synopsis Sword Art Online: Alicization - War of Underworld
To fully understand War of Underworld , you should follow this sequence: Sword Art Online: Alicization - War of Underworld
Episodes 1–24. Ends with the battle against Administrator.