Alice taking up her duty as a defender of humanity.

The broadcast of War of Underworld was a globally anticipated event that faced significant challenges. The first half of the arc aired in Japan from , with global simulcasts on platforms like Crunchyroll and Funimation. The second half of the arc, originally scheduled for an April 2020 premiere, was delayed due to the COVID-19 pandemic. It ultimately aired from July 12 to September 20, 2020 . In the United States, the English dub aired on Adult Swim's Toonami programming block.

It moves beyond "trapped in a game" to explore the ethics of AI, the weight of memories, and what it truly means to have a soul. Connecting the Dots: Real World vs. Underworld

Here is a breakdown of what makes War of Underworld a must-watch, even for those who fell off the SAO wagon years ago.

(Episodes 1–12)

: While Chapter 1 follows the first half of the anime faithfully, the game branches into its own unique storyline after the fight with Quinella, though it later incorporates "War of Underworld" themes and characters through updates and DLC.

As Kirito becomes more entrenched in the world of Underworld, he learns about the sinister forces threatening the land. The primary antagonist, the Pope of the Central Cathedral, seeks to exploit the Fluctlight technology for his own gain, sparking a catastrophic chain of events. Throughout the arc, Kirito forms alliances with Eugeo, Alice Zuberg, and other characters, as they work together to prevent a disaster that could have far-reaching consequences.

Availability varies heavily by region, but many international territories include War of Underworld in their anime catalog.

Major Themes

Sinon (as Goddess Solus) and Leafa (as Goddess Terraria) join the fray, alongside thousands of players from ALfheim Online and Ordinal Scale who log in to support their friends. Themes Explored in the Arc

A-1 Pictures spared no expense here. The animation quality is film-tier for much of the season. The battle sequences are grand in scale, featuring thousands of soldiers, dragons, and magical artillery. The "Integrity Knights" shine in battle, showcasing distinct fighting styles and magical abilities that make every skirmish feel dynamic.

Following the battle with Quinella, Kirito is left in a comatose, soul-damaged state. Alice brings him back to her hometown, Rulid Village, to protect him. However, peace is short-lived. The Subterranean gate collapses, allowing the forces of the Dark Territory—including goblins, orcs, and dark knights—to invade the Human Empire. Alice must take up her sword, rally the remaining Integrity Knights, and fight a desperate holding action against overwhelming odds. The Real-World Front (The Ocean Turtle)

On a deeply psychological level, the "link" is the only mechanism capable of saving Kirito from his catatonic state.

This is why SAO fans argue that War of Underworld is the most "hard sci-fi" season yet. It treats the internet as a tangible place where souls can meet—and fight.