Chiaki Chigira (千明 ちあき, Chigira Chiaki) is a Level 4 Burst Linker currently belonging to the Mathematics and Martial Arts Research Club (or "Enbuken") at Seibi Academy. She is one of the club's two freshman members, along with Lilya Usachova, and is one of the main characters of Accel World/dural: Magisa Garden.
Chiaki was born and raised for a time in Japan, but after the death of her older brother, later revealed to have been a Burst Linker named Glass Monarch, her family moved to the U.S. for business reasons. He left her with many fairy tale-esque stories of a warrior queen named "Snow Black," or Kuroyukihime, and his last words were a wish for her to grow strong and meet her for real.
While living in America, she trained in as many different martial arts she could find, excelling in all of them, including karate, parkour, sambo, and pankido. However, she eventually outgrew all of these and sought out greater strength. She moved back to Japan on the first day of school in the year 2047 and enrolled at Seibi Academy, where she was quickly recruited by Enbuken and became a Burst Linker.
Chiaki has long, black hair and purple eyes. Relatively short compared to the other characters, she is usually seen wearing her school uniform, a reddish-purple dress. She also wears fingerless gloves all the time. Like Kuroyukihime, she also has two strands of hair sticking out like a butterfly's antenna.
Chapters 1 through 5
After enrolling at Seibi Academy, Chiaki continues her mission to strengthen herself, but none of the martial arts-related clubs on the campus can come close to her level of skills. While at a loss over what to do next, she is approached by the two current members of the Mathematics and Martial Arts Research Club, abbreviated as "Enbuken," Kurumi Kuruma and Yuuko Hoori. After being brought into the club, which is essentially only a front for their Brain Burst activities, Yuuko attempts to install Brain Burst on Chiaki's Neuro Linker, only to find that it's already there. After briefly interrogating her and coming to the conclusion that she didn't know it was there at all, they all enter the Accelerated World for a match.
There, they all get to see Aluminum Valkyrie for the first time. Four other Duel Avatars then appear – a self-titled "tribe" from Seioh Academy – and challenge the new Burst Linker to a duel. Chiaki faces off against Seioh's new member, Zircon Paladin, and wins quite easily.
She's later introduced to the school's local network, and Kurumi and Yuuko explain the basics of acceleration and the blue world to her. Yuuko gives Chiaki a "proper" avatar, then Chiaki spots a rabbit avatar and chases it (due to Yuuko having programmed in cat-like instincts to her costume). However, try as she might, the rabbit avatar outruns her.
The next day, Chiaki tells Yuuko and Kurumi that she won thirty straight duels in Brain Burst the night before. However, the rabbit avatar appears to be her true objective. She logs into the school's network and starts chasing the rabbit again. Eventually, the rabbit has nowhere to go, and after it jumps as high as it can, Chiaki catches it on the way down. After they land, she immediately logs out and goes to meet the girl behind it – a Russian girl named Lilya Usachova. She accepts Chiaki's invitation to join Enbuken, and later on, Yuuko gives her Brain Burst and becomes her parent.
When they go to look at Lilya's Duel Avatar, Iris Alice, Seioh challenges them again. Zircon Paladin wants his revenge on Aluminum Valkyrie, but Chiaki refuses, stating that she gained so much experience the other night battling that it wouldn't be fair.
Chapters 6 through 11
After having practiced more and spent more time with Lilya, they both go to Kurumi and Yuuko and say that they want to do a tag team duel. Chiaki has been preparing for this for a few days now and promises that she will "awaken" Iris Alice. When they get into the battle, their opponents are Ash Roller, a member of Great Wall, and Vanilla Slicer, one of the members of Seioh's "tribe." After Valkyrie brushes aside Roller without a second thought, she throws Alice straight at him and knocks him off his bike.
However, the real threat is twofold. One, if Valkyrie loses this duel, she would lose the rest of her Burst Points; Kurumi and Yuuko hadn't talked to her about what that means yet because they're still amazed she got to level 4 in just a few days. Chiaki isn't willing to step down, though. The other threat is Vanilla Slicer, who has learned of Valkyrie's weakness from a fellow Burst Linker, Ruddy Raccoon, one of the only ones to defeat Valkyrie. Slicer uses his Special Attack, Vacation Plan, to put her to sleep, rendering her useless.
He would like to kill her, but Roller doesn't like this plan anymore, so Slicer puts him to sleep too. When Valkyrie is about to be killed, Chiaki shouts out to Lilya in Russian for her to get up and do what she needs to do. After a rather long, inspirational speech in Russian, Lilya activates her Special Attack by breaking her bottle item, creatively named Little Bottle, and transforms into a gigantic monster, proceeding to win the match single-handedly.
Though they may have won, Chiaki then faces off against Yuuko (Orange Raptor), and Yuuko fires a Deca Flare at her as punishment for not bringing her "parents" in on her plan and letting them help. Chiaki and Lilya later walk home and share some taiyaki on the way.
Chapters 14 through 18
A week or so later, Chiaki is approached by Yuuko, who takes her into the Unlimited Neutral Field. Their goal is the shop "Burlone," located on the top of a giant, moving turtle Enemy. They pick out some clothes to give to Iris Alice, and then Chiaki explains why she knew Lilya was strong all along over some frozen yogurt.
Later on, Valkyrie and Alice win another tag team duel, and Alice levels up to 2. Yuuko and Kurumi explain the level-up process to her, and Yuuko tells her to pick the most fun level-up bonus. Kurumi reassures Chiaki, though, that focusing on a specific goal when raising your Avatar is a valid way to have fun since that's what she's been doing.
Lilya decides on her level-up bonus soon after, and they go into a duel setting to look at it. Valkyrie and Raptor give her the clothes they picked out, and then Alice shows off her new Enhanced Armament, Queen's Astrology.
Chapters 19 through 21
While Noriko sneaks into Enbuken's clubroom, Chiaki is drawn into a challenge with Yuuko in a 2D fighting game where the loser takes off one piece of clothing each time. Chiaki loses badly but is eventually saved by Kurumi.
Soon after, Kuroyukihime herself pays a visit to Seibi Academy, and Chiaki, without thinking, channels all of her parkour skills and rushes out to meet her as she approaches the main building. Then, she remembers that Burst Linkers aren't supposed to show themselves to one another, and quickly retreats, embarrassed.
A while after that, Lilya is almost ready to get to Level 4. Lilya ends up challenging Zircon Paladin, who still only wants his revenge on Valkyrie. Lilya manages to get Paladin to promise to pay ten times the average amount of Burst Points, as they're both on the verge of being able to level up to 4 safely. Paladin, overconfident, completely loses to Iris Alice's incredible maneuverability and a one-two punch from her Queen's Astrology, shattering Paladin's ambitions of becoming a King one day.
Chiaki's Duel Avatar is a rare metal-colored type. As her properties are aligned with those of aluminum, her body is light but fragile, which suits Chiaki's current fighting style. However, she is frail to indirect attacks, like those from Yellow-color Avatars.
Its design places emphasis on wing-like decoration, such as the small wing parts on her head and her cape.
Aluminum Valkyrie's parent is Glass Monarch, her late older brother – the Brain Burst program was given to Chiaki at the hour of his death.
- Mode Alloy – An Ability that changes the properties and appearance of her armor. Each mode is named after a valkyrie.
- Mode Alloy with Kára – First shown by her clone during the Legion Formation Quest.
- Mode Alloy with Reginleif – A fire-resistant mode. First used to counter Orange Raptor's Deca Flare.
- Mode Alloy with Hildr – A mode that strengthens her armor, powerful enough to shatter one of Glass Monarch's fully-levelled Centurions.
- She studied Russian for two months in the Unlimited Neutral Field.
- She appears on the front cover of a manga in Toaru Kagaku no Railgun S Episode 4.
- She and her Avatar appear on the front cover of Accel World dural: Magisa Garden 01
- Accel World/dural: Magisa Garden volume 1
- Accel World/dural: Magisa Garden volume 2
- Accel World/dural: Magisa Garden volume 3