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Unital Ring IV (ユナイタル・リングIV,Yunaitaru Ringu IV?) is the 25th book in the Sword Art Onlinelight novel series, published on December 10, 2020. It is the fourth volume in the Unital Ring Arc.
The curtains finally rise on the fated battle against Mutasina from the 《Virtual Research Society》 ――
The chance encounter with Eolyne, the masked man with the same eyes and voice as his late friend, has left Kirito in a state of deep shock. Yet the boy does not have the luxury of drowning in sentimentality as compounding incidents transpire in two virtual worlds concurrently.
"Perhaps this could be the onset of a new otherworlder war"
An omen of another upcoming unrest befalls 《Underworld》 after 200 years.
Meanwhile, the fated battle against Mutasina from the 《Virtual Research Society》 draws near in 《Unital Ring》. Under her lead is a battalion of a hundred players, bound under her rule by the horrifying 《Choker of the Damned》 suffocation spell. On the opposing side, Kirito and co plan their next moves in order to turn the tables on the overwhelmingly unfavourable situation, but――
Cordial Chords (2017, OS BD/DVD) - Distant Journey (2019, Alicization BD/DVD Vol.1) - If We Could Walk Together (2020, Alicization WoU BD/DVD Vol.8) - If You Were Here (2019, Alicization BD/DVD Vol.8) - If You Wish It (2020, Alicization WoU BD/DVD Vol.2) - Rainbow Bridge (2014, Extra Edition BD/DVD) - Sugary Days (2015, Season 2 BD/DVD Vol.5) - Sisters' Prayer (2015, Season 2 BD/DVD Vol.9) - The Day After (2013, Season 1 BD/DVD Vol.9) - The Day Before (2012, Season 1 BD/DVD Vol.1)
Girl Meets Gun ~P90 ni tsuite Yoku wakaru Online (PYO)~ (2018, P-90 Airsoft Gun bonus) - Her step, step (2019, ReoNa's Prologue Album) - Minami no Island Online (MIO) (2018, Dengeki Island!) - MZO (2016, Dengeki Splash) - Pitohui, Elsa, and a Fine Day for Handguns (2021, AM.45 Airsoft Gun) - Sugoimizugi Jam (2015, Dengeki Girls Swim Wear Festival) - The Untold Tale of the Vorpal Bunny's Birth ~Otherwise Known as the Worries of Two Gun Nuts~ (2020, Vorpal Bunny Airsoft Gun bonus)
Idle Talk - The Shinobi's Reckless Remarks (2017, Dengeki Bunko Magazine Animate bonus) - The Story of the Matchmaking Bakeneko (2016, Clover's Regret Vol.1 Animate bonus) - The Strange Tale of Makuwa Melons (2016, Clover's Regret Vol.1 Melonbooks bonus)
Melodies Go Beyond the Forgetting Curve... - The Grand Plan for a Summer Festival Performance! - The Grand Plan to Overcoming Picky-Eating! - When Asuna and Yuuki Changed into Swimsuits (2015)
Ichiban Kuji Ordinal Scale
A Brief Instant of Reminiscing Right Below the Concert - From Asuna's Diary on a Certain Day in Late April (2017)
SAO x KYOTO NIPPON FESTIVAL
The Great Barrier of the Old Capital of Kyoto (2019)