Academia

 Academia' (アカデミア Akademia) is a mysterious school in the Yu-Gi-Oh! ARC-V'' anime that trains "Duel Soldiers" and is located in the Fusion Dimension. It is run by Reo Akaba under the guise of "The Professor", a man originally from the Standard Dimension, and serves as his base of operations.''' The goal of Reo Akaba and as such the goal of the Academia, is to use the power of Fusion to make all the worlds become one. In order to accomplish this, Academia employs its army of Duel Soldiers in order to conquer the other Dimensions by turning its inhabitants into cards. This goal is referred as "ARC Area Project".

Strategies
In Episode 40, Serena mentioned that Barrett is using a "By-The-Books" strategy, a kind of strategy used by the Academia.

Recruitment
Once children graduated from elementary school, they are sent to Academia to learn and become Duel soldiers for the completion of the ARC Area Project. Once sent to Academia, nobody was allowed to leave until graduation. Those who escaped will be pursued by the Juvenile Officers to be taken back and punished accordingly. After Yūshō's arrival, those who escaped Academia are taking shelter at Yūshō's underground Duel school.

Past
Three years prior to the ARC-V storyline, Reiji Akaba had unknowingly traveled to Academia via an interdimensional transporter. He eventually met Serena, who he helped escape from faculty members who were pursuing her, only to have them both caught by Reo and several members of Obelisk Force, the elite vanguard squad. Reiji was confused by the ensuing discussion about alternate dimensions and the Academia, until the squad hauled Serena off and placed a device on Reiji's wrist, which sent him back to Standard.

At some point, Reo ordered his elite vanguard squad to advance into the Xyz Dimension and attack, as part of his plan to eventually unite the Four Dimensions. Without warning, they did so, causing chaos with powerful monsters like "Antique Gear Chaos Giant" and sealing nearly all of the inhabitants of Heartland City in cards in the process. Yūto, Shun, Ruri and a few others were the only survivors of the attack including, although Ruri was captured some time later. They were also able to wipe out most of the Resistance  and without any Duels, the soldiers would seal innocent people into cards.

Pre-Maiami Championship
During his Duel with Shingo, Yūto asked about the connection between Leo Duel School and the Academia. However, Yūto soon discovered that most of LDS knew nothing.

Round 1
After Shun Dueled Sora, it is implied that the latter was affiliated with the Academia, as Reiji mentioned they could learn more about it from Sora. During his Duel against Yūya, Yūto revealed that the Academia attacked the citizens of Heartland and sealed them in cards. During this time Sora was transported back to the Academia due to a program on his Duel Disk that activated after revealing his goal of acquiring a powerful Fusion Monster. When Sora came back, Reo had his men check Sora's memories as to find out why Sora had been returned since Standard were not their enemies. From Sora's memories, Reo found out about Yuzu whom he called the "Fourth Piece" he needed and ordered Yūri to bring her to him.

Round 2
While Sora was recovering in the nursery he protested to go back to Standard since there were Xyz Remnants there, Serena eavesdropped on his demands and planned to go to Standard as to prove her strength to Reo in order to be at the frontlines. Several guards attempted to stop her but failed, but Barrett decided to go with her instead of stopping her since it was his duty to protect her. The two arrive at Standard and Serena watches Hokuto perform an Xyz Summon on screen, believing him to be part of the Xyz Remnants, she manages to find him and easily defeats and transforms him into a card. Serena then turns his attention into Yū Sakuragi a prominent Xyz User, in the Maiami Championship. Unfortunately for her, Reiji found about her appearance and correctly deduced she would attack Yū, so he used him as bait to lure the duo.

Barrett vs. Reiji
Serena and Barrett encountered Yū, but before they could attack him, Reiji appeared and ordered Yū to leave, while having Nakajima seal the area so the Academia duo could not escape. Serena attempted to Duel Reiji but Barrett offered to Duel instead, since it was his duty to protect her. Serena stood aside and watched. Barrett and Reiji Dueled, with Reiji noticing that Barrett was a war veteran, as Barrett used burn tactics to rapidly damage Reiji. Barrett praised Reiji for using his own Life Points to maintain the cost of his "Covenant" cards, mentioning that he deserved a war medal for that. Reiji defeated Barrett using a combination of "DDD Marksman King Tell" and "DDD Oracle King d'Arc". Serena attempted to leave, but Reiji stopped her and the two reminisced on their past encounter years ago. A barely conscious Barrett activated his Duel Disk to return to the Fusion Dimension and to give away Serena's location. Reiji offered Serena the chance to join him into defeating Reo, but Serena refused, saying that all she wanted was to earn Reo's recognition. She left, but not before Reiji declared her an enemy should she interfere with him.

Battle Royal
After receiving the transmission, Reo had a meeting with Sora, who requested to be sent back to the Standard Dimension. Reo agreed to Sora's request, but ordered him to look for Serena and make it his priority to bring her back. Sora noted Serena's resemblance to Yuzu and asked why the two looked alike. Reo replied that he did not need to know that and had the Obelisk Force accompany Sora. The Obelisk Force entered the Standard Dimension during the Maiami Championship's Battle Royal, prompting Reiji to cut any transmission that featured the Academia. Sora encountered Shun, Yūya and Knight of Duels students. Sora had the Obelisk Force deal with the Knights while he Duels Shun on nearby ruins. The Knights of Duels were then swiftly defeated and sealed into cards. Seeing this, Yūya became infuriated and challenged the three soldiers to a Duel. Meanwhile, Reiji sent his Junior Force of Lancers, led by Yū.

The Obelisk Force vs. Yūya
While Yūya Dueled against the Obelisk Force "Dark Rebellion Xyz Dragon" to attack them. The trio of soldiers began to panic but they were unable to defeat Yūya, who used "Synthesis Magician" and "Antithesis Magician" to Pendulum Summon "Odd-Eyes Pendulum Dragon" and then used the Pendulum Effects of both his Pendulum Monsters to grant "Dark Rebellion" a Level equal to the Level of "Odd-Eyes". Yūya overlaid his two monsters to Xyz Summon "Odd-Eyes Rebellion Dragon the Supreme King Black Dragon" and used its effect to destroy their monsters, inflict effect damage and attack a number of times equal to the monsters destroyed. This defeated all three soldiers in one fell swoop.

The Obelisk Force vs. the Youth Lancers and Yūgo
More Obelisk Force soldiers entered the Volcano Area and spotted Serena with Dennis Macfield and Yuzu. They escaped, leaving Yū and the rest of the Youth Lancers to fend off the invaders. However the Youth force was quickly overwhelmed and turned into cards. Before Yū was defeated, Yūgo interfered in the Duel after recognizing the Academia soldiers as people he met before. He defeated the soldiers by using their "Antique Armageddon Gear" against them with a combination of his "Clear Wing Synchro Dragon" and "Synchro Cracker" to destroy all monsters with lower ATK than "Clear Wing". Yū realized that he could not fight any further and ran away in a panic without thanking Yūgo, annoying him. Nakajima expressed his concern to Reiji that the Youth Force were unable to repel the invaders and Reiji acknowledged the LDS did not have the strength to fight the Academia, but that his plan for the Lancers was for them to master Pendulum Summon as a new power that could give them an edge in battle. He referred to the potential Duelists as the "Yūya Sakaki Generation".

Academia's goal
While the battles were taking place, Yuzu and Serena talked, and Serena revealed that the Academia, under orders of "The Professor", plotted to make the Four Dimensions become a single world, calling it an "honorable goal". However, Yuzu revealed the truth of the Academia's cruel assaults into other dimensions to Serena and requested for her to seek the truth by meeting Shun, the Xyz remnant she was looking for, to which Serena agreed. Knowing that the Obelisk Force were hunting Serena down, Yuzu suggested they swap clothes so that Serena could meet Shun and confirm the truth.

Yūri meets Yuzu
Dennis, now revealed to be an agent working for the Academia, eavesdropped on their conversation and met Yūri, telling him of the girls' plan so that he could track Yuzu. During this time, Halil and Olga appeared, mistaking Yūri as an opponent for the Battle Royale, and challenged him to a Duel. Yūri was annoyed, but he accepted their challenge. He easily defeated both of them and sealed them into cards. The Obelisk Force surrounded Yuzu, believing her to be Serena, but Yūri interfered and ordered the soldiers to retreat or he would seal them into cards as well.

He threw the cards containing Halil and Olga at them, causing the soldiers to leave. Yūri tried to convince Yuzu to surrender, claiming it was pointless to fight and that "the Professor" needed her. Yūri challenged Yuzu to a Duel, which Yuzu was forced to accept. Yūya and Gongenzaka, who were looking for Yuzu, encountered Dennis and told him of the attacking soldiers, unaware of his true colors. Dennis maintained his facade by agreeing to accompany Yūya and Gongenzaka. Meanwhile, Yuzu was forced to run for her life after knowing that she was no match for Yūri, who was in hot pursuit with "Starve Venom Fusion Dragon". Before Yūri could find her, Yuzu's bracelet activated teleporting Yūri away, due to Yūgo's arrival. Yūgo mistook her for Rin. Before Yūya could find her, the bracelet shone once more and teleported the two away leaving Yūya, Gongenzaka and Dennis unable to find her. Dennis incorrectly believed that Yūri had finished his mission.

The Obelisk Force vs. Tsukikage, Serena, Shun, Michio, Teppei and Shingo
Serena, who managed to avoid the Obelisk Force, witnessed Shun being defeated by Sora and thrown downstairs, leaving him injured. Serena activated "Lunar Eclipse" so that the two of them could escape. Sora initially mistook Serena for Yuzu and ordered her to stand aside. Upon recognizing her Duel Disk as being of Academia origin, Sora pursued the pair. The three eventually reached the Volcano Area with Sora requesting to get his "prey". However the two Fuma Ninja students, Tsukikage and Hikage appeared and blocked Sora's path. Hikage decided to face Sora, allowing Serena, Shun and Tsukikage to escape. Dennis, observing from afar, encountered remnants of the Obelisk Force. He told them that Serena was in disguise. The three soldiers asked Dennis if he wasn't coming, but Dennis said he couldn't because there were "too many cameras". The Obelisk Force soldiers then attacked Serena, Shun and Tsukikage, and forcing them into a Battle Royale. Shun wanted to go first, but Tsukikage interfered and fended off the attacks of the three soldiers using "Barrier Ninjitsu of Gathering Shadows". Serena decided to go next and Fusion Summoned "Moonlight Cat Dancer". Before it could attack, the Obelisk Force used "Fusion Dispersal" to counter her monster and damage her, as they prepared for her. Michio Mokota and Teppei Tairyōbata then joined the Duel, but suffered a 2000 LP penalty. Using a combination of "The Legendary Fisherman III" and "Monster Pie" the two were able to damage the entire Obelisk Force for 2000 LP each one. The Obelisk Force used a combination of "Antique Gear Reborn", "Antique Gear Spark Shot", "Antique Gear Booster" to deal enough damage to defeat Michio and Teppei, who were weakened by the penalty. Both were sealed into cards afterward. Before Tsukikage could suffer from the same fate, Shingo appeared and used "Flame Guard" to protect him, having heard the situation from Reiji, but took the 2000 LP penalty. Yūya and Gongenzaka could only watched as Sora sealed Hikage into a card. Gongenzaka then saw Serena, who he mistook as Yuzu, in a Duel and left to help her. Yūya was left alone and challenged Sora to a Duel in order to return his smile. Sora agreed, since he did not like having a losing record against Yūya.

The Obelisk Force defeats by Revolution Falcon
Gongenzaka arrived as Shingo used "Abyss Actor - Devil Heel" and "Abyss Actor - Funky Comedian" to Pendulum Summon "Abyss Actor - Big Star" and used its effect to search and equip it with "Abyss Script - Fantasy Magic in order to return the Obelisk Force's "Antique Gear Triple Bite Hound Dog" to the Extra Deck and break their combo. However, the Obelisk Force used "Antique Gear Rebirth Fusion" to Fusion Summon "Antique Gear Ultimate Hound Dog" and used its effect to halve the Life Points of all their opponents. Gongenzaka took his turn, and used a combination of Pendulum Summon and the effects of two of his "Superheavy Samurai Thief" and a copy of "Superheavy Samurai Courier" in order to provide Shun with the Pendulum Cards that Shingo activated previously. Shingo questioned his move because he thought he could break the combination by himself, but Gongenzaka said it was fine this way. Shun asked why Gongenzaka went so far to give him Pendulum Cards. Gongenzaka replied that Shun was the one who would finish the Duel. During his turn, Shun remembered all the people who protected him during this time, and found the notion ridiculous. Shun used "Devil Heel" and "Funky Comedian" to Pendulum Summon three copies of "Raid Raptors - Wild Vulture" and used them to Xyz Summon "Raid Raptors - Revolution Falcon". Shun used its effect to let it attack all the Obelisk Force's monsters. Its other effect allowed Shun to reduce their ATK and DEF 0 during battle. "Revolution Falcon" attacked and defeated the remaining Obelisk Force soldiers, winning the Duel for Shun and his allies.

Sora vs. Yūya
Meanwhile, Sora and Yūya perform their Duel with the two trading blows. Yūya was convinced that Sora had become warped and revealed his intentions to bring him back to his "usual self", but Sora refuted this by saying that the Sora that Yūya knew was never his true self; his true self was a soldier of Academia. Yūya disagreed because he remembered that Sora had fun during their first Duel. Sora retorted that he was not being serious back then, but Yūya claimed his smile was genuine and that the two became friends after that Duel. Sora told Yūya that there were things more important than friendship. Yūya denied this by pointing out that Sora taught Yuzu how to Fusion Summon as a sign of friendship, but Sora claimed he did so merely because Fusion Summon was an honorable mechanic and a power that could make the worlds become one. Yūya argued that fusing the four worlds was wrong, but Sora angrily stated the opposite. Yūya asked Sora if he was aware of the cruelty inflicted into the Xyz Dimension by the Academia, and Sora indifferently stated that it couldn't be helped to achieve the Academia's goals. An infuriated Yūya told Sora that they didn't have the authority to fuse the worlds. Yūya Xyz Summoned "Dark Rebellion Xyz Dragon" and used its effect on Sora's "Death-Toy Scissors Tiger", but Sora used "Death-Toy March" in order to negate the effect and Fusion Summoned "Death-Toy Sabre Tiger", which subsequently revived the previously destroyed "Death-Toy Scissors Bear". The effects of both "Tiger" and "Sabre Tiger" boosted the ATK of Sora's monsters to colossal levels. Yūya then used "Synthesis Magician" and "Antithesis Magician" to Pendulum Summon "Odd-Eyes Pendulum Dragon". He used the effects of both Pendulum Monsters to make "Dark Rebellion" have the Level of "Odd-Eyes" and overlaid both of his Dragons to Xyz Summon "Odd-Eyes Rebellion Dragon the Supreme King Black Dragon" Yūya used its effect to destroy both "Tiger" and "Bear" since their Levels were lower than 7. Sora used "Fusion Front Base" to avoid the effect damage. At this point, Sora regained the same excited demeanor he had during his first Duel with Yūya because Yūya was able to Summon an Xyz Pendulum Monster, while finally realizing that battling Yūya is fun. Yūya agreed to his statement that Duels were meant to have fun. Yūya used the effect of "Rebellion Dragon" to attack as many times as monsters were destroyed by its effect. Sora activated "Flame Chain" to lower its ATK, but Yūya countered with "Flame Power" to boost its ATK. The two raced for an Action Card, but were unable to catch it since the Battle Royale timer expired, disabling the "Wonder Quartet" Field Magic and ending the Duel without a result. Gongenzaka and the others, who witnessed the Duel, caught up to Yūya. Yūya mistook Serena for Yuzu until Serena revealed she was not Yuzu. Sora, knowing the mission had failed, activated his Duel Disk to be transported back to the Academia.

Shun vs. Dennis
After the Battle Royale incident, Serena defected from Academia after hearing the truth of their crimes from Shun. The officially established Lancers, made to counter Academia, started their own plans to increase their effectiveness by traveling to the Synchro Dimension in order to recruit allies, though they never knew that Dennis was an Academia spy. Upon arriving at the dimension, Dennis and Gongenzaka were separated from the others. They were scouted by Gallager for his underground Dueling and both met up with Shun, who was part of the underground Dueling circuit. Dennis Dueled Shun, and his Dueling prowess made Shun suspect his identity. Dennis, Shun, and Gongenzaka were arrested, but escaped and was forced to participate in the Friendship Cup.

Friendship Cup
During the course of the Friendship Cup, Reiji heard information from Tsukikage that Security's director, Jean-Michel Roget had apparently came from another dimension and that he brought with himself advanced technology and quickly raised the ranks of Security, while using Gallager in order to recruit strong duelists for himself. This information, along with the use of a Fusion Monster by Duel Chaser 227, made Reiji suspect Roget was actually an agent of Academia. During the last Duel of the first round of the Friendship Cup, Shun was set to battle Dennis, and the latter secretly vowed to destroy the former slowly. Shun had suspicions that Dennis was a member of Academia and he focused on unmasking Dennis. The two started an aggressive Duel, and through the use of "Raid Raptors - Target Flag", Shun forced Dennis to reveal his hand, showing a "Fusion" card. Dennis then used "Antique Gear Chaos Fusion" in order to Fusion Summon "Antique Gear Chaos Giant", confirming his Academia roots and declaring the start of a hunting game. "Chaos Giant" rendered Shun's combination useless, but he was able to survive the attack of "Chaos Giant" with "Raid Raptors - Last Strix". Regardless, the attack on "Revolution Falcon" laid waste to the arena, debris being thrown everywhere. Enraged after learning about Ruri's kidnapping from Dennis, Shun counterattacked by using "Rank-Up-Magic Soul Shave Force" to Summon "Raid Raptors - Satellite Cannon Falcon". This monster reduced the ATK of "Chaos Giant" to 500. Dennis attempted to survive using Action Cards, but the debris from the attack of his own "Chaos Giant" tripped up his D-Wheel and he was unable to and was thus defeated by "Satellite Cannon Falcon". After the Duel, Dennis admitted that Shun had won before passing out. Still filled with rage, Shun tried to seal Dennis in a card but was unable to do so, so instead he attempted to punch Dennis but was stopped by the tournament's staff, who then carried Dennis off on a stretcher.

Friendship Cup Finals
Dennis was being taken to the recovery room when the Executive Council and Security both attempted to take him into custody. Sora saved him and took him away to an alleyway. He explained to Dennis that he was attempting to capture Serena as per the orders of the Professor, and sent Dennis back to Academia to recover from his injuries. After hearing Dennis' report that Yuzu and Serena were in the Synchro Dimension's City, Reo gave Barrett a new mission to go to the Synchro Dimension with the Obelisk Force and capture Yuzu and Serena. He also informed him that Yūri would also come to the Synchro Dimension.

Arriving at City
Near the end of the Duel between Crow and Yūya, Sora noticed the Obelisk Force on several gliders with searchlights and warned Crow about it. The Security and Reiji also noticed this, and Roget ordered Sergey to defeat the Obelisk Force instead, putting aside his plan to retake control of Reiji and the Executive Council.

Obelisk Force vs. Sergey & Reira
Once landed, the Force split up into groups of three, searching for Yuzu and Serena. Those who were to find either of them would alert the others with a red flare. Serena, still incapacitated from Security's attempt to take her and with Tsukikage and Reira Akaba, was found rather quickly and a flare was lit, slowly drawing the Obelisk Force to her location. Several members then entered duels with Reira, with all of them ending up defeated by the young boy. Others approached the Executive Council's building, which was under siege by Security as well. However, Sergey Volkov intercepted them, defeating several members, much like Reira did.

Obelisk Force vs. Tsukikage & Sora
Around the same time, another trio found themselves halted by Tsukikage whom they quickly overpowered with their numbers. They held the upperhand until Sora joined the duel on Tsukikage's side, much to their surprise. This trio was then defeated after Sora, with help from Tsukikage, destroyed their "Hound Dogs" and turned them against their masters. All of the defeated Obelisk Force members were recalled to Academia near-instantly.

Academia vs. Yūya, Yūgo, and Sergey
Yūya arrived to assist Reira, defeating three Obelisk Force. Barrett then arrived with another group of Obelisk Force and Dueled Yūya. Barrett's Beastborg combo prevented Yūya from attacking, activating spell cards, and summoning monsters, cornering the latter as Barrett interrogate him for Yuzu's location, something that Yūya refused to tell. Sora arrived and took out the Obelisk Force who came with Barrett, but was followed Yūri with another group of Obelisk Force. Before Yūri could Duel with Sora, Yūgo arrived and Yūri decided to Duel him instead, immobilising Sora. The Duel was interrupted by Yuzu's arrival who transported Yūri and Yūgo, and then Sergey who swiftly defeated Barrett, but Barrett successfully brought back Serena with him using the last of his power. With Barrett defeated and Yūri disappeared, the remaining Obelisk Force decided to retreat.

Heartland City
Academia students are still in the Xyz Dimension and continue to hunt down people. Three students manage to corner a man and proceeded to seal him into a card. They also find a family in hiding with Yūya, Gongenzaka, and Shingo. The six of the them prepared to Duel, but the students doesn't recognize the Duel Disks and learn that Yūya, Gongenzaka, and Shingo are Lancers and their mission to stop the Interdimensional War. The students tell them its their mission to finish the ARC Area Project. Yūya tells the hardships he went through and defeats them in a combined Pendulum Summoning with Gongenzaka and Shingo. After defeating them Shingo tries to seal them into cards as payback but is stopped by Yūya. The three students escape only to into Kaito Tenjō, who sealed them into cards.

Juvenile Officers vs. Asuka Tenjōin
Yuzu, who got transported to Fusion Dimension, witnessed a group of people being sent to Academia at the dock. It's revealed that as Serena had said before, Academia are gathering Duelists throughout the dimension to be trained as Duel soldier to complete ARC Area Project. Once Duelists are sent to Academia, they are not allowed to leave and those who attempted to do so will be recaptured and punished. Yuzu, who got mistaken as a runaway, was chased by Juvenile Officers, but was fortunately saved by Asuka Tenjōin, who took her to You Show Duel School, an independent Duel School created by Yūshō that sheltering Duelists who have escaped from Academia.

Edo Phoenix vs. Yūya
An Academia member, Mamoru Noro, was restless over Edo's absence, the Commander-in-Chief of Academia for the invasion of Xyz Dimension, and protested how they were late to complete the ARC Area Project in Xyz Dimension, worrying the Professor will got mad if they keep prolonging it. Meanwhile, Edo was looking for Yūshō Sakaki whom he had a grudge against. However, he instead encountered Yūshō's son, Yūya, who was also in the middle of looking his father. Once knowing Yūya's connection with Yūshō, Edo brutally attacked Yūya with intention of making him a bait to lure out Yūshō. Edo at first got the advantage, until Yūto possessed Yūya's body to take over the Duel and countered attack, forcing Edo to end the Duel with a draw.

Three more students were sealed into cards by Kaito after being defeated in a Duel.

Yuri vs. You Show Students
Yuri, who returned to Fusion Dimension, encountered a few of You Show Duel School students while they were escorting another Academia Duelist who escaped. He managed to turn one of them into card. Two of the students escorted the escapee to their hideout while the remaining five stayed to avenge their friend who was carded. Despite the advantage in numbers, Yuri easily defeated all of them in his second turn using the combination of his spell card and his ace monster, turning all five of them into cards. He once again encountered Yuzu with Asuka after hearing the attack, but before he could challenge them, Yugo arrived, which activated Yuzu's bracelet and transported him away.

Tyler Sisters vs. Allen & Sayaka
After receiving report that Lancers have arrived in Heartland, Reo dispatched the Tyler Sisters, Gloria and Grace, to eliminate them. At Heartland, the sisters encountered a Resistance Duelist, Sayaka Sasayama, and mistook her for Lancers. Allen Kozuki then arrived and together with Sayaka, accepted their challenge for Tag Duel. The Sisters' combo easily overpowered Allen and Sayaka, leading to the Resistance Duelists' defeat. Before the sisters could card them, Shingo and Gongenzaka arrived, revealing themselves as Lancers. Unsatisfied with the previous Duel, the sisters challenged the two of them to another Tag Duel.

Technology
Their technology is advanced enough to create brain scanners that can access to one's memory. They are also shown to have interdimensional travel technology, as well as abilities to materialize Duels and technology to seal any human into cards.