Sword Art Online: Season 4
2019 · 23 episodes · ★ 7.9
Sword Art Online Alicization: War of Underworld
What Season 4 of Sword Art Online
Six months after the defeat of Administrator, Alice lives with Kirito in Rulid Village, the town where she grew up. Kirito remains catatonic after a short circuit damaged his fluctlight during the assault on the Ocean Turtle, RATH's marine platform. Distrustful of the Axiom Church, Alice has brought him there and hopes he will wake up. But peace doesn't last. The Dark Territory begins to invade the Human Empire, and Alice takes up her role as Alice Synthesis Thirty to defend the world Kirito and Eugeo fought for. The season pits Alice against a threat she can no longer avoid, while Kirito struggles to recover.
Season 4 Episodes
4x01 In the Far North
Six months have passed since the fierce battle against Administrator. Alice has brought Kirito to her childhood home, Rulid Village, where they live peacefully. Gazing out at the world that she saved with Kirito, Alice reflects on all that’s happened.
Directing: Takashi Sakuma · Writing: Muneo Nakamoto · Starring: Tasuku Kida, Takayuki Ishii, Hidemitsu Shimizu, Hikaru Tanaka
4x02 Raids
A force from the Dark Territory is attacking Rulid Village. Though she’d lost her purpose in battle, in order to fight for her family, and for the people that Kirito and Eugeo tried to protect, Alice takes up the Osmanthus Blade once again!
Directed by Takehiro Miura · Written by Muneo Nakamoto · Starring Kanehira Yamamoto, Haruki Ishiya, Kenta Sasa, Tsuguo Mogami
4x03 The Final Load Test
The mysterious group that attacked the Ocean Turtle turns out to be a secret unit under orders from the U.S. National Security Agency. And its leader, Gabriel, has battled Kirito and Sinon before.
Directed by Hiroshi Kimura · Written by Muneo Nakamoto · Starring Akira Ishida, Kiyomitsu Mizuuchi, Ikuto Kanemasa, Shinya Takahashi
4x04 Dark Territory
Shasta, commander of the Dark Territory's dark knights, had intended to use Administrator's death as a chance for peace with the Human Empire. But his plans are thwarted by Emperor Vecta's return to the land of darkness.
Directed by Takashi Sakuma, Naomi Nakayama · Written by Yukito Kizawa · Starring Rie Kugimiya, Shinya Takahashi, Sayaka Senbongi, Hiroki Goto
4x05 The Night Before Battle
Resolved to fight for humankind, Alice joins the forces of the Human Empire, bringing Kirito with her. But while the forces of darkness boast overwhelming numbers, only thirteen Integrity Knights are available to fight for the Human Empire.
Directing: Tomohisa Onoue · Writing: Yukito Kizawa · Starring: Hikaru Hanada, Masashi Yamane, Takeaki Masuyama, Hitomi Nabatame
4x06 Battle of the Knights
The Final Load Test has begun, and the Eastern Gate has collapsed. Incited by Gabriel, now Emperor Vecta, the massive army of the land of darkness pushes on towards the Human Empire.
Directing: Takuma Suzuki · Writing: Yukito Kizawa · Starring: Hikaru Hanada, Mirei Kumagai, Kanako Sakuragi, Shoko Yuzuki
4x07 Stigma of the Disqualified
Integrity Knight Renly Synthesis Twenty-Seven, in battle for the first time, flees his position, allowing goblins from the forces of darkness to infiltrate to the tent where Kirito is.
Directing: Yuya Horiuchi · Writing: Kohei Urushibara · Starring: Maaya Sakamoto, Hina Kino, Konomi Kohara, Ryota Suzuki
4x08 Blood and Life
The powerful formal art unleashed by the Integrity Knight Alice inflicts severe casualties on the forces of darkness. Alice encounters an enemy survivor and learns that Emperor Vecta's objective is to find the "Priestess of Light."
Directed by Shunsuke Nakashige · Written by Muneo Nakamoto · Starring Takeaki Masuyama, Saori Onishi, Daichi Endo, Fumiko Uchimura
4x09 Sword and Fist
Upon seeing Alice, Gabriel orders his entire army to capture her. The pugilists guild races ahead of the main force. As Alice and Bercouli try to come up with a strategy to counter them, the silent Integrity Knight Sheyta Synthesis Twelve steps forward.
Directed by Hiroshi Kimura · Written by Kohei Urushibara · Starring Maaya Sakamoto, Akane Ouchi, Ryosuke Hara, Takayuki Ishii
4x10 Stacia, the Goddess of Creation
Asuna has logged into the Underworld using the superuser account of Stacia, the Goddess of Creation. After she descends, she is reunited with Kirito, thanks to Ronie and Tiese. But soon Alice arrives, leading to a precarious situation!
Directing: Takashi Sakuma · Writing: Kohei Urushibara · Starring: Ryo Sugisaki, Shinya Takahashi, Takayuki Ishii, Ayako Kawasumi
4x11 Heartless Choice
Asuna has created a bottomless chasm. The dark knights and the pugilists attempt to cross over to the other side, where the Human Empire Army waits. Meanwhile, Critter releases an announcement about a limited-time beta test for a bizarre new VRMMO.
Directing: Akira Yamada · Writing: Muneo Nakamoto · Starring: Ayana Taketatsu, Maaya Sakamoto, Shinya Takahashi, Fumiya Tanaka
4x12 Ray of Light Mid-Season Finale
Due to Gabriel's scheme, U.S. players were given black knight accounts, and are now continuously logging in to the Underworld. They begin mercilessly slaughtering soldiers from both the Human Empire Army and the Dark Territory Army.
Directing: Shunsuke Nakashige, Kenji Seto · Writing: Muneo Nakamoto · Starring: Shinya Takahashi, Naoto Kobayashi, Fumiya Tanaka, Kei Minegishi
4x13 The War of Underworld
Sinon has logged in with the super-account of Solus, the Sun Goddess and rescues Asuna and the others at the last minute. Meanwhile, Leafa logs in with the super-account of Terraria, the Earth Goddess, and descends to the Underworld.
Directing: Masakazu Obara · Writing: Kohei Urushibara · Starring: Robert Waterman, Hikaru Tsuchizaki, Fumiya Tanaka, Kei Minegishi
4x14 End to Eternity
Despite its modest size, the Human Empire Army and Asuna valiantly battle the wave of American players surging towards them. But they’re hopelessly outnumbered, and the Human Empire soldiers start to fall one after another.
Directing: Toru Hamasaki · Writing: Kohei Urushibara · Starring: Maaya Sakamoto, Nobuyuki Kobushi, Atsushi Tamaru, Hitomi Nabatame
4x15 Instigation
Bercouli pursues Vecta, who’s abducted Alice. After a long, vicious battle, Bercouli unleashes his secret sword skill, Uragiri, and finally defeats Vecta, despite having sustained severe injuries himself.
Directing: Takehiro Miura · Writing: Muneo Nakamoto · Starring: Shiori Izawa, Kenta Miyake, Asami Tano, Takumu Miyazono
4x16 Code 871
The traitor inside Rath turns out to be a researcher named Yanai. When Higa attempts to restore Kirito, Yanai tries to thwart the operation by holding him at gunpoint. Meanwhile, in the Underworld, Sinon confronts Gabriel, who has logged back in.
Directed by Takashi Sakuma · Written by Kohei Urushibara · Starring Sayuri Yahagi, Chiwa Saito, Yu Shimamura, Daiki Yamashita
4x17 Prince of Hell
Asuna and the others succumb to Vassago and the Chinese/Korean players. Discovering the catatonic Kirito, Vassago kicks his wheelchair over. Enraged, Klein lunges at Vassago, only to be pinned down by enemy players. Just then, someone unexpected appears.
Directing: Akira Yamada · Writing: Muneo Nakamoto · Starring: Yoshitsugu Matsuoka, Yusuke Numata, Nobuhiko Okamoto, Ren Kato
4x18 Memories
Sinon manages to severely damage Gabriel, but her strength has been sapped. Leafa collapses after wiping out the American players. And Asuna, her situation now hopeless, gazes at Kirito. But the Black Swordsman continues to wander through his dreams.
Directed by Yuya Horiuchi · Written by Muneo Nakamoto · Starring Saori Hayami, Soichiro Hoshi, Aoi Yuki, Yoshitsugu Matsuoka
4x19 Awakening
Escaping his nightmares, Kirito regains consciousness at last. With the Night-Sky Blade in his right hand and the broken Blue Rose Sword in his left, he faces off against Vassago, armed with the Mate-Chopper, now enormous in size.
Directed by Shunsuke Nakashige · Written by Kohei Urushibara · Starring Aoi Yuki, Megumi Han, Kaori Ishihara, Reina Kondo
4x20 The Night-Sky Blade
Alice and Asuna head to the World’s End Altar as Kirito confronts Gabriel. Unless he can defeat Gabriel and return to the real world before the maximum-acceleration phase begins, Kirito will have to spend the next 200 years in the Underworld.
Directing: Masakazu Obara · Writing: Muneo Nakamoto · Starring: Maaya Sakamoto, Sakura Tange, Junichi Suwabe, Mutsumi Tamura
4x21 Beyond Time
The maximum-acceleration phase has begun. Alice successfully logs out of the Underworld, but Kirito doesn’t make it in time. In the real world, Higa and Kikuoka rush to shut down the STL, in order to disable the maximum-acceleration phase, but…
Directing: Tomonari Tanaka · Writing: Muneo Nakamoto · Starring: Koichi Yamadera, Akira Ishida, Yoji Ueda, Yasunori Matsumoto
4x22 Alice
The “Rath Attack Incident,” masterminded by the American National Security Agency, is over. Now head of the newly formed Oceanic Resource Exploration & Research Institution, Rinko unveils Alice to the world as an authentic artificial general intelligence.
Directing: Akira Yamada · Writing: Muneo Nakamoto · Starring: Ayahi Takagaki, Yoshitsugu Matsuoka, Ayana Taketatsu, Rina Hidaka
4x23 New World Season Finale
Rinko informs Kazuto that Alice is missing. He’s about to rush to the Rath Roppongi branch when the doorbell rings. In a panic, Kazuto throws open the door, only to find a deliveryman there with a huge cardboard box.
Directed by Takashi Sakuma · Written by Muneo Nakamoto · Starring Yoshitsugu Matsuoka, Ayana Taketatsu, Shunsuke Sakuya, Aya Endo
Season 4 Cast
Haruka TomatsuAsuna (voice)23 episodes
Isshin ChibaCritter (voice23 episodes
Junya EnokiLilpilin (voice)23 episodes
Sanae KobayashiRinko Koujiro (voice)23 episodes
Ayahi TakagakiRika Shinozaki (voice)23 episodes
Miyuki SawashiroSinon (voice)23 episodes
Tsuyoshi KoyamaVassago (voice)12 episodes
Junichi SuwabeBercouli (voice)12 episodes
Shinya TakahashiMale Reporter (voice)11 episodes
Mutsumi TamuraRenly (voice)11 episodes
Reina KondoLaurent Ney (voice)10 episodes
Naoyuki AgeishiRed Soldier (voice)7 episodesAll Seasons
Season 12012 · 25 ep. · 
Season 22014 · 24 ep. · 
Season 32018 · 24 ep. · Where to Watch Season 4 of Sword Art Online
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Frequently Asked Questions
How many episodes does Season 4 of Sword Art Online have?
Season 4 of Sword Art Online has 23 episodes.
When did Season 4 of Sword Art Online premiere?
Aired October 13, 2019.
Where to Watch Sword Art Online Season 4
With a subscription on Amazon Prime Video, Crunchyroll, Crunchyroll Amazon Channel and Amazon Prime Video with Ads (availability may vary by country).
What is the best episode of Season 4?
According to the TMDB user rating, episode 4x19, "Awakening," has a 8.9.