Like the other new Union leaders, he was given a book with laws set by Ava. However Brain has declared he wishes to use the book to achieve a personal goal of his, wanting to be the virus that will alter the events set in stone.
Brain has black spiky hair that droops down over his eye. He wears a black coat with rolled up sleeves, gold buttons, and a large collar, grey pants, and black cowboy boots. His face is concealed by a black fedora that sports a black feather with a tan streak down the middle.
During the progress of the chapters, Brain's face was revealed, sharing a close physical resemblance of teenage Master Eraqus.
Before Kingdom Hearts Union χ
Four years before the Keyblade War reached its conclusion, Master Ava chose Brain to be the fourth Union leader but he reacts negatively to it, feeling like not being cut out for the job. Asking why Ava made the decision, it was ordered by the Master of Masters where Brain assumes the job is going to be difficult. Brain knows that the Union leaders are supposed to meet up after the Keyblade War, and asks if he cannot do so prior, assuming that he's being used as pawns in someone else's game.
Brain is not fully sure of the decision, but Master Ava questions to him that what if the world's fate was already decided. This shocks Brain, seeing as no fun invovled, but Ava counters his opinion of knowing what's going to happen, bringing the Book of Prophecies to the topic. Ava says that if Brain knew what the future held, it would be able to be changed, whereas Brain wonders if the changed event would be written in the book, or would be overwritten every now and then, but not even Ava knows about it.
Ava theorizes if the outcome would lead to a completely new future, which would also happen if their inevitable fate gets altered. She gives a copy of the Book of Prophecies to Brain, tasked by the Master and shows the list of the five planned Union leaders to Brain, with his name circled out on it, and warns Brain to not let everyone else read it. She puts the list in between the pages of the leaders' fates before giving the book to Brain, aware of that he knows the basics. Brain also promises to not open the Book if he can avoid his fate, where Ava respects his decision, making her aware that when Brain will know the time to use it.
Brain first meets Ephemer, Skuld and Ventus at the Badlands in the Data World, after the conclusion of the Keyblade War, where he reads up on the rules that were given by the Master of Masters, and somewhat disagrees with them but ends up handling them anyway.
After the Union was formed, they made their way to the Clock Tower where the Foretellers reside. Brain presents the first task to the new Union Leaders from the Book of Prophecies, where they create Spirit Dream Eaters of their own to commemorate their promotion as Union Leaders and to forget about the tragic events of the Keyblade War. Brain and Lauriam both put together the equipment needed to create spirits while the others search for materials to create them.
During a meeting discussing about Shift Pride, the act of Keyblade Wielders turning against each other, Brain sees it as friendly competition despite others, but Ventus and Skuld strongly disagrees with him, where the latter remembers that fighting against one another in a team could fill their Heart with Darkness. Ephemer agrees at first, but believes that he should fight against Data versions of Keyblade Wielders instead so they won't hurt anyone, upon Lauriam's suggestion, and to which Brain agrees with.
When Lauriam returns to the Clock Tower about Strelitzia's whereabouts, Brain suggests that she was looking for the Player to invite them to join the Dandelions before the bells had rang and as she wasn't at Fountain Square during the speech, she went to the Keyblade War and was hesitant for the Player to join before Strelitzia.
While studying the Book of Prophecies further, Brain lifts up his hat, and comes up with a plan to avoid the Data World's Keyblade War, so he plans to become a virus and overwrite the system. He heads to the Control Room, where he uses the computer and ends up glitching parts of the world and causing holograms of humans from the real Daybreak Town to appear and Heartless which brings to others finding out about the truth.
Ventus, Ephemer and the Player find Brain inside the Clock Tower's control room and ask what is happening. He tells them that Keyblade wielders were able to visit worlds in the future via the Book of Propechies, as it was capable of projecting the future while they also could have visited present versions of the worlds by land. The worlds had broken up after the Keyblade War, and were recreated as Data so their futures could still be accessible virtually. Despite that, the Dandelions had continued to visit the virtual worlds via the digital Daybreak Town even before the Keyblade War.
Brain suddenly starts to question if the Daybreak Town they're in is real or a virtual reality, where Ephemer believe that it is real even though unexpected things are happening, which brings Ventus to believe that the world is virtual. Brain is still confused on the world's status, thinking that the world feels real even though there are glitch effects happening everywhere.
He finds out that it's connected to a world called Game Central Station that doesn't exist in this dimension or time period, after he linked the world to the Daybreak Town computers, despite not knowing the true cause of it. Despite the others warning about the task being too dangerous, Brain sends Ephemer, Ventus, and the Player to Game Central Station in order to stabilize the route so others can come and go.
During the expedition, Brain discovers that the data Daybreak Town and the worlds associated with it existed before the Keyblade War had happened, while he theorizes that a connection to the real world is possible from them despite them virtually recreated. When Ventus and Lauriam explain their encouter with glitchy figures of Ava and Strelitzia, Brain finds out that the new world that was connected is aware that their world is created virtually, and concludes that Daybreak Town they're in is all data.
This shocks Ventus and Ephemer, and asks if the real Daybreak Town still exists but Brain doesn't know, except that they were in the real world before the Keyblade War came to a close. Skuld asks Brain if there was a way back, but won't be easy for him to do so and asks the others to give him some time. Brain also thinks that it was a setup by somebody, and this data world was made to be cut off from the real world all along.
Despite putting together his reasons, Brain still doesn't fully know why it is happening. He goes out of the room to accomplish his goal on becoming a virus, and studies on the Book of Propechies more. A few minutes later, Lauriam meets up with Brain in the Fortellers' Room where he finds out that before Strelitzia disappeared, she knew that the Keyblade War was coming, which was likely why she didn't want to join the Dandelions.
Brain says that the Dandelions knew about the Keyblade War, but wonders why Strelitzia knew about it. Lauriam is curious to why she convinced the Player to join the Dandelions, while Brain wonders that something made her sure that the Keyblade War was going to happen after all. Thinking of a promise he made to Master Ava before the union was formed, Brain comes up with an idea and orders Lauriam to leave him alone.
Looking through the Book of Prophecies, Brain discovers a depressing truth, so he summons his Chirithy for the first in a long time and asks her to gather the Union leaders to the hilltop to dicuss it in private. Ephemer learns about Brain's becoming of a Union leader on the hilltop from Master Ava, bringing up that she brought him there as well. He also learns that he was chosen to be the holder of the Book of Prophecies in order to recreate the world and keep gathering light.
Brain shows the note of the listed Union leaders with his name circled on it, where Ephemer learns that Brain wasn't the one that was supposed to handle the Book of Prophecies and Strelitzia was supposed to become a Union leader rather than Lauriam as her name was crossed out. Master Ava was also the person that decided to give the Book of Propchies rather than the Master of Masters, hoping that the future contained inside would be changed.
In order to find out more about the unexpected change, Brain opts to talk with Lauriam. Ventus and Skuld make their way to the meeting point, where Brain asks who told them to be Union leaders. Both of them respond with Master Ava, while Brain asks where they met her, with Skuld responding on the hilltop, but for Ventus, it was near the Clock Tower. In fear of both of them being suspicious of Brain, he tells them that he was given the Book of Prophecies and about the mix-up in the names to the person handling it.
When talking about Strelitzia's sudden removal from the list, Brain says that the decision may have to do with Master Ava's involvement with the former's absence but doesn't fully believe because Ava wouldn't do it. Skuld asks if the replacement was considered after Strelitzia's disappearance, but it makes no sense to Brain because she was last seen before the Keyblade War had started, trying to get the Player to join the Dandelions.
Brain assumes that she heard that Ava chose her to be a Union Leader and that the war was coming, and if Ava wanted to make a sudden change in plans, she would have told somebody. He further states that he was trusted with the Book of Prophecies and list of names, if a change were to happen. Thinking further about the decision to tell Lauriam the truth, he and Ephemer remain cautious about it in order to not cause any conflict, but he tells that Ventus' name wasn't on the list of Union Leaders.
After Ventus is shocked to find he wasn't on the list, but joined as part of the team, Brain becomes doubtful of Ava as she would be the kind of person to keep Strelitza safe rather than being sent into the front lines without any prior knowledge. This makes Brain question why they were chosen as Dandelions, with Ephemer reciting to keep the Light alive but also realizes that Darkness would be along the way, and could be found anywhere.
Skuld questions Brain that Darkness may have been hidden within Ava, which brings to him asking Ventus if she noticed anything strange with Master Ava at the Clock Tower. His response plays out exactly like the time when the union was formed at the Badlands, but she told him to visit an old, abandoned house before noticing a mysterious figure exactly like Strelitzia. Later, Ephemer thinks that Stretlitzia's disappearance was caused by Darkness itself, where Brain agrees with him on.
Ephemer questions Brain if Darkness is watching the Union leaders, where he doesn't know much but agrees with the idea, stating that it could be putting its plans into motion much like what happened to Strelitzia. An unconcious Lauriam overhears the conversation, and begs Brain to explain the full truth about Strelitzia's disappearance. Instead, Brain says that Lauriam is experiencing the emotions of fear, doubt and anger from Lauriam, which would potentially lead to turning on one another in the Union.
When Lauriam calms down, Brain was about to tell the truth but is interrupted by Ventus who puts the blame on himself. Brain and the others try to stop Ventus from making himself the victim, where he manages to change his ways but Darkness emerges from him. When learning about Ventus' internal motives for power, Brain asks Darkness why he possessed Ventus, finding out that it was decided that he would harbor darkness and had a vessel chosen for Darkness itself from the Book of Prophecies.
Finding out that Darkness itself read the Book of Prophecies while it was being written and remembering the important parts, Brain also discovers that the force and the Master of Masters were once friends. They also existed all along and came to fruition when it was acknowledged, but only in the form of one being. Brain and the others decide to fight against Darkness itself in hopes of vanquishing it, except that it proves to be futile for the Union.
Brain questions Darkness itself, where he assumes that they're desperate to get into their business and must be a reason why they're here. He learns that Darkness can be easily spread to the data world, but they all try to get back at them for possessing Ventus' body and causing conflict among the Union leaders.
When the Player comes back from Game Central Station to fight against Darkness, they all learn that the data Daybreak Town is falling into darkness because one of the lifeboats were activated by Maleficent, which also goes the same for the real world. While Lauriam feels that they're being used like pawns, Ephemer doesn't believe so and believes that Master Ava would never treat them badly, and Brain believes in their leader. Thinking they had won, Darkness is unable to be defeated due to lacking a form while the Darklings attempt to attack Ventus, but his revelation of being pure light manages to temporarily repel them.
After Lauriam learns of Elrena's Chirithy spotting somebody in a black coat taking a person that looked like Strelitzia, Brain is unsure of who the person is but notices that the Master of Masters shouldn't be here, even if it were the real world. This brings to him noticing that there could be data versions of the people that situated in the real Daybreak Town, including that of the Union leaders and Strelitzia.
Brain also theorizes that somebody managed to access Strelitzia's data based on the glitched figures that was seen in the abandoned house, which further frustrates Lauriam. Brain is also confused considering that all of the Masters aren't present, but Lauriam suggests they would be able to find answers in the real world. Brain decides to head to the basement to take the lifeboats in order to make their way back, despite being mildly worried about its fate.
When they get to the basement, they notice that two of the lifeboats have been taken leaving room for only five to get back to the real world. Brain looks on the computer of data Daybreak Town's current status, which is slowly turning into a glitched mess by the minute and need to act as quick as possible to escape. Worrying about the rest of the Keyblade Wielders in the world, Brain says that they will go to sleep, as if a computer enters sleep mode.
Brain further explains that the Master of Masters knew about the worst case scenario and created a data version of Daybreak Town in the event of such disaster, and that the world can be virtually rebooted and restored to it's former self. Even if they make it back to the real world via the lifeboats, they will have to use it again despite having no knowledge of where they'll end up. Brain starts to doubt the decision, realizing that if nobody goes back, then no one will know what happened back in the data world and are unable to be rescued.
Brain decides to take one of the lifeboats and hopes to find a way to save everyone, but also decides to save one left over in hopes of saving the other three. When the lifeboats open up, Brain bequeaths his duties to Ephemer, including his own Keyblade and Book of Prophecies. Ephemer accepts the offerings from Brain but still believes that they belong to the latter because Ava entrusted him with them. He makes his way to one of the lifeboats and successfully escapes the digital world.
Back at the real Daybreak Town, Brain tries to figure out a way to bring back everyone via the original transfer system between the real and data worlds but is worried about not having enough time. However, he thinks of another suggestion to bring back the three that was left in the data Daybreak Town rather than everybody else.
Brain tells Lauriam and Elrena to get into the lifeboats as quickly as possible if he wants to save Ephemer, where he will send the remaining two lifeboats into the data world as part of the plan. Lauriam wonders if they will be fine, but Brain says that his heart is connected to Ephemer and everyone else.
While Brain and Lauriam bid farewell to one another before the the latter gets into the lifeboats, they hope that their duty as a Union leader is etched onto the latter's heart. Brain hopes that Lauriam will be able to see Strelitzia again, as Lauriam says the same for meeting Brain.
A sudden tremor happens when the lifeboats were being sent, where Brain ends up encountering a hooded figure named Luxu. Brain assumed that Luxu disappeared before the Unions were formed, but the former ends up asking if he is a Union leader. After Luxu asks Brain what happened to the other leaders, including Lauriam being struck down, Brain explains the plan of sending the two pods back into the data world to save the rest and says he would be staying in this era to awaken the Dandelions in the data world.
Taking Master Ava's explaination of sleeping wielders in the data world, Luxu ends up truthfully saying that the data Daybreak Town was a cage built to trap the darkness and once consumed it cannot escape. Luxu further explains that the lifeboats are incomplete and requires someone to build the form at the destination, while Brain notices that he hasn't completely read that part. Brain says that he's going to spend his life to fulfill his role, but Luxu thinks of it as a bad idea. He escapes Daybreak Town before the two lifeboats containing Ephemer and Skuld made it back to the real world, which would end up being torn apart by darkness.
An Unfamiliar Town
An unknown amount of time later, Brain later finds himself in Scala ad Caelum where a mysterious hooded figure named Sigurd knows of Brain and gives his hat back to him that had gotten lost. After Brain introduces himself, Sigurd goes on to take him to HQ so it can be explained further while reciting the events Brain's getaway from Daybreak Town and arrival in Scala ad Caelum, and fated meeting.
Brain is confused at Sigurd's sudden knowledge and planned encounter, and also asks where is everyone else that had escaped with him, but Sigurd says that he is the only one that has arrived in the era. Along the way to HQ, Brain notices a statue of Ephemer where Sigurd explains that it was built in honor of the first Keyblade Master and for founding Scala ad Caelum. Relieved to see him being represented as an honor, Brain is happy to say that he knows him as a best friend.
- In Kingdom Hearts III's secret reports 11-13, an unknown author implied to be Luxu notes that one of the new leaders was an imposter and calls them a 'virus in the program'. Brain later refers to himself with this exact term in a cutscene in Union X. Despite this, it was later revealed the Brain was not the impostor.
- While Brain was originally meant to be union leader, he was not meant to receive the book of prophecies. Master Ava gave him the book instead along with the original list of new union leaders and the name of who actually was supposed to receive the book.
- When Lauriam confronts Skuld about his sister, Strelitzia's, disappearance, Brain points out inconsistencies in Lauriam's story as if he is suspicious of him.
- Although Brain later reveals Strelitzia was supposed to be the union leader, he admits he doesn't know what happened to her.