Mayuzumi Takumu (黛 拓武, Mayuzumi Takumu?) is a childhood friend of Arita Haruyuki and Chiyuri. Originally, he was aligned with the Blue Legion, Leonids, but eventually switched over to the Black Legion, Nega Nebulus, after his defeat by Haru.
Takumu is friendly with Chiyu and Haru and was shown to be kind and well-mannered. Haru looked up to him as a role model and mentor whenever they battled in Accel World together. He is shown to be wise and knowledgeable when it comes to the Brain Burst program, and during battles, he can deduce the most sensible strategy. After joining Nega Nebulus, he calls Kuroyukihime "master" as a sign of respect. His caring way has him trying to stop or resolve arguments which are usually between Kuroyukihime and Yuniko. However, his knowledgeability and kindness are also where some people, such as Yuniko and Kuroyukihime, allow them to make jokes or insults towards him like calling "professor" or "four-eyes." He takes these seriously and becomes depressed.
Taku, Haru, and Chiyu were childhood friends when they were younger and still were as they grew older. During that time, Chiyu decided to be in a relationship with Taku who was happy that she chose him. Despite the relationship, the three of them were still close friends. He was excellent in kendo as he won many tournaments and also had perfect scores in school (however, it is revealed later on that it was in fact because of the Brain Burst program that he abused).
After Kuroyikihime was hospitalized, Taku and Haru figure out each other's true objectives and identities. During their fight, Taku reveals his feelings about how Haru would always get between him and Chiyu and that she would care more about him instead of her boyfriend. However, after their battle, the two made up and started their friendship from the beginning once more along with Chiyu.
With Kuroyukihime's help, Taku can realize his true self and decides to join Nega Nebulus to help their cause and Haruyuki as well.
Takumu has light brown hair and blue eyes. When he was initially seen in the series, he had on his school uniform which was different compared to Chiyu and Haru as he went to a different school than the two of them. His school uniform consisted of a dark gray coat with the same colored pants. He was also seen carrying his kendo equipment.
After joining Nega Nebulus, he transferred to Haru's school, and his school uniform now consists of a lighter blue blazer with a white shirt underneath and a green tie. He has weak eyesight, which he used to correct using the vision correction feature of his Neuro Linker. He now wears glasses as he told Kuroyukihime that he wanted to see the world with his own eyes.
Return of the Black Snow Princess Arc
- Main article: Return of the Black Snow Princess Arc
Return of the Black Snow Princess (Side Story)
- Main article: Elements (Side Stories) Arc
Crimson Storm Princess Arc
- Main article: Crimson Storm Princess Arc
Dusk Robber Arc
- Main article: Dusk Robber Arc
Flight Towards the Blue Sky
- Main article: Flight Towards the Blue Sky Arc
Later on, Cyan Pile participates alongside Nega Nebulas in the «Hermes Cord Trasversing Race». In the next volume, he acts as a messenger between real life and the Accelerated World in operation to rescue the ex-Nega Nebulas member Ardor Maiden due to being a pure CQC specialist with no capabilities to avoid the fierce attacks of Suzaku, one of the four Gods guarding the Imperial Palace.
He is one of the few players who receive the «Incarnate System Study Kit» from Magenta Scissor. Soon afterward, he is assaulted by the Player Killer group «Supernova Remnant», which has a contract paid with real money on Silver Crow and is forced to fight a «Sudden Death Duel» in the same conditions as he fought Dusk Taker. As he is about to lose, he asks for a chance, and he is given one. Upon equipping the ISS Kit, he obtains access to its abilities and easily defeats and uninstalls the five enemies.
Regretting it, the next day he confronts Haruyuki demanding to defeat him. At this point, the ISS Kit has already manifested and starts to control his emotions and thoughts via nightmares, even when he takes his Neurolinker off, appearing in the form of an eye in his «Pile Driver». After an intense fight, where Silver Crow manages to equip an arm of the pure form of the Disaster Armor, «The Destiny» and counter his darkened IS skills with his own, the ISS Kit attempts to infect Haruyuki, to which Takumu reacts by using «Lighting Cyan Spike» on his neck, putting an end to the fight before Silver Crow was also infected.
Upon realizing that even with the neurolinker off the ISS Kit could still affect him, they decide to have a sleepover at Chiyuri's house to keep watch on him. After realizing that Lime Bell's «Citron Call» wouldn't be effective, they decide to direct link before falling asleep.
At the main server of Brain Burst, when Haruyuki manages to destroy the ISS Kit plaguing him with his new Incarnate Skill, «Laser Lance», instead of running he confronts the darkness of its main body head on, using «Cyan Blade» to damage it before they finally wake up, with a completely purged Takumu.
Takumu's avatar resembles a tin man. His whole body is covered tin with a cone-shaped tin hat on top of his head.
Takumu's Brain Burst character is Cyan Pile. Cyan Pile's appearance is very similar to a knight. His body is metallic, heavily armored and on his shoulders are two protruding crystals.
His face is covered by a kendo mask and possesses a large body as a result of his desire to become a swordsman, yet his intense fear of thrust attacks after he was bullied is what led him to own the Enhanced Armament «Pile Driver».
Cyan Pile's main abilities lie in his main weapon which is a pile driver-like, spear cannon that he can materialize at will onto his right arm.
- Perforation: The passive ability of the «Pile Driver». Has a third gauge which until recharged prevents Cyan Pile from attacking via launching his metallic stake.
- Cyan Spike: The metallic spike on Cyan Pile's right arm fires at his opponent to a short distance but has deadly accuracy. This ability is a Normal Activation-type ability that does not consume Killer Gauge.
- Lightning Cyan Spike: Cyan Pile's Level 4 Killer Move; the Pile Driver's spike travels farther and has more piercing power.
- Splash Stinger: The panel on Pile's chest opens and fires multiple spike-like projectiles at his enemy.
- Spiral Gravity Driver: Pile draws a magic circle in the air with his spike that turns his spear cannon into more of a smash cannon that can be used to break through multiple walls or floors at once, as shown in his battle against Silver Crow when he uses it to propel Crow through 9-10 floors. This is also the only time Cyan Pile has used this skill during the anime.
- Cyan Blade: This is a second-qrant firing range expansion-type "Incarnation Skill". After training with Scarlet Rain for a time, Pile learned to use the power of incarnation. To activate this skill, the spike on Pile's cannon glows blue, he pulls the entire cannon off and shapes it into a katana (Japanese Sword). Obtained after he learns to use incarnation after his first fight with Dusk Taker.
- Accel World Anime, Episode 10
- Accel World Anime, Episode 7