Axel was the trump card for the rest of the Organization as a double agent in Castle Oblivion to keep track of Marluxia's plans. In Kingdom Hearts II, Axel betrayed the Organization for his friendship with Roxas and acted of his own accord to try and help Sora, though he originally wanted to turn Sora into a Heartless to get Roxas back. Axel appears in Kingdom Hearts 358/2 Days as a playable character in Mission Mode and as Roxas's and Xion's best friend.
Lea, his complete being's original name, was revealed in the Day 356 Secret Report and also mentioned by Saïx. Lea was friends with Saïx's original persona, Isa. Lea, Isa, and Axel each appear in Kingdom Hearts Birth by Sleep, Axel's appearance merely a cameo.
Kingdom Hearts 358/2 Days & Kingdom Hearts: Chain of MemoriesEdit
After inducting Roxas into the Organization, Xemnas places him under Axel's tutelage. Initially, Axel was unsure how to treat Roxas, as he acted like a "zombie" due to the lack of memories of his previous life. Over time however the Nobodies begin to bond, eating sea-salt ice cream together at the Twilight Town Train Station after missions. As their friendship grows strong, Axel began to demonstrate emotions due to his time with Roxas. Axel is also present when Xion joins the Organization, but is sent to Castle Oblivion to deal with the traitorous Marluxia. Having received these orders through Saïx, the second-in-command to Xemnas, it would appear that Axel also planned to eliminate other members who could stop their plans to overthrow the Organization.
In Kingdom Hearts: Chain of Memories while Sora and Riku wandered around in Castle Oblivion, Axel worked for the two parties of the already divided Organization in the castle. One side, Marluxia and Larxene, sought to use Sora's powers to usurp Xemnas and the rest of the Organization while using Naminé to alter Sora's memories. Those who stayed in the castle basement were Vexen, Lexaeus, and Zexion—three of the original members of Organization XIII. The three realized Marluxia's ambitions and tried to counteract by using a replica of Riku to destroy Sora. At first, Axel joined the rebel group, though his intentions at that decision point remained unclear.
Upon throwing the first battle with Sora, Axel admitted to testing the Keyblade master's strength. Being the first Organization member to reveal his face, Axel gave up a card created from Sora's memories for him to progress further in the castle. After leaving Sora bewildered, Axel holds a serious conversation with Larxene in which he professes an interest in the fact that Sora retains his self-consciousness even after becoming a Heartless.
After Vexen nearly reveals the existence of Roxas to Sora, Axel was ordered by Marluxia to dispose of him. Axel did so effortlessly, and was at last accepted by Marluxia and Larxene into their conspiracy. Using this to his advantage, Axel allowed Naminé to escape and contact Sora. He later confronted Marluxia, allowing him to figure out that he acted as a double agent during their entire time in the castle. Citing his previous order to rid the Organization of traitors, Axel readied to attack Marluxia, even after Marluxia used Naminé as a shield, but was interrupted by Sora, whom he eventually fought for the last time. At the end of the battle, Axel pretended to be defeated and confused Sora with the words "It was worth saving you after all," and vanished.
After his battle with Sora, Axel met with Zexion in the castle basement. Zexion brought up the subject of Riku and requested data on Destiny Islands in the form of a card. Despite their previous collaboration, Axel later offered Replica the honor of eliminating Zexion, promising the duplicate that he would gain new powers and be able to defeat the real Riku by taking them from Zexion. The exact reason for Axel's betrayal is not stated, and seems self-contradictory after he had helped stop Marluxia's betrayal, though it was true that both sides of the Organization members in Castle Oblivion had their own ideas for betrayal. Axel commented that it would be more interesting to see Sora and Riku's future than to save Zexion; however, this may have had something to do with Axel's friendship with Roxas, which could have been the reason why he effortlessly destroyed Vexen—to prevent either Sora or Roxas from meeting.
In Kingdom Hearts Re:Chain of Memories, Axel stated the reason for his betrayal of Zexion, saying: "You just found out way too much." This seems to be quite ambiguous, as in Kingdom Hearts Re:Chain of Memories Axel and Zexion were shown to be friendly with each other (e.g. in one scene it was shown that Zexion and Axel were making bets on which Organization members in the Castle would be the next to die, something that Axel wins when he accurately predicts that Marluxia will be the next to fall), however this could mean Zexion found out about Saïx and Axel's plan to take over the Organization.
When Axel returns to The World That Never Was, he feels that Roxas has replaced him with Xion since he was told everyone at Castle Oblivion was terminated. Axel becomes jealous, not sure exactly what to make of Xion. At Roxas's suggestion, the three begin to spend time together as a trio. Some time later, Axel finds himself before Saïx, and reveals that he regrets not being able to talk with Saïx as he could with Roxas and Xion. Saïx reminds Axel of the friendship they shared before becoming Nobodies, and the plans they had to take over the Organization to regain their hearts.
After discovering who and what she was, Xion began wanting to leave the Organization. Axel eventually catches her in front of Roxas despite his pleas. With him and Roxas not on speaking terms, Axel soon becomes torn between his attempt to save them both from Xemnas's intent to do with any one of them. While assigned to a mission in Wonderland, Xion runs off and Axel makes no attempt of stopping her once she knocks out Xigbar. A few days later, with Roxas learning of Xion's identity and that Axel kept it from him, he also leaves the Organization. Axel, who has enjoyed the time he spent with his best friend, is distraught by Roxas' decision as he tried to reason with him to keep him safe.
The next day, under orders, Axel tracks Xion to the Old Mansion in Twilight Town where he realizes her intentions, telling her that he's fed up with her and Roxas being selfish and doing whatever they want, before he manages to knock Xion unconscious in their battle. But the fight took its toll as Axel faints from fatigue once he brings her back to the Castle That Never Was, with Xemnas taking Xion from him. Later, in his quarters, learning of the aftermath of Roxas and Xion's fight, a depressed Axel discovers a popsicle stick which reads "WINNER", a gift left by Roxas.
Kingdom Hearts IIEdit
Axel is sent to DiZ's Digital Twilight Town to bring Roxas back to the Organization; however, his first effort failed due to DiZ's appearance and the restarting of the Twilight Town program. Roxas was dumbfounded by Axel's appearance, lacking any memories of him and awareness of what was going on. Pressed by the threats by Xaldin and Xemnas, Axel again tries to recover Roxas without destroying him, keeping in mind the Organization's order to either eliminate Roxas or be destroyed himself. Roxas learns that the two had been best friends from Naminé and mentions this to Axel, but his bluff is called when he is unable to remember "their boss's name." DiZ then intervenes and Roxas escapes for the Twilight Town mansion. The two meet again at this mansion in the computer room basement. Despite Roxas's recovery of his memories, Axel is hurt from his previous encounter with Roxas and fights him and his dual Keyblades. Axel loses the fight and disappears, choosing not to carry out his mission.
While Sora reawakens with Roxas inside him, Axel is entrusted by Riku to protect Naminé. Naminé's words, about those who are dear to them despite being Nobodies, strangely moved Axel.
During Sora's exploits to the different worlds, Axel appeared before Kairi on a beach across Destiny Islands, intending to kidnap her to draw Sora out. Axel's plan was simple; if Sora were to become a Heartless again, then Roxas would be reborn. However, Kairi escaped through a Corridor of Darkness created by Riku and landed in Twilight Town where she stayed for some time in wait of Sora. Axel, however, followed her to the town and stole her away again, but not long afterward she was taken captive by Saïx who was under orders to give Axel something to actually worry about. After the invasion of Radiant Garden by the Heartless, Sora confronted Xemnas, the leader of the Organization. Xemnas decided to take his leave and Axel later greeted Sora. Axel hinted that the Keyblade caused the hearts that composed the Heartless to flee, but refused to say what Organization XIII would do with those hearts. Sora realized that Axel is Kairi's captor, and Axel confirmed this. Though initially seeming unrepentant for his actions, he soon apologized for kidnapping Kairi, and made a hasty exit when Saïx appeared.
On the way to The World That Never Was, Sora, Donald, Goofy, and Mickey are trapped in Betwixt and Between by Nobodies, but Axel arrives to help. Sora and Axel battled the Nobodies, but seeing that the Dusk's numbers were too great, Axel decided to put his entire being and essence into an attack, destroying the Nobodies but sacrificing himself in the process. He did this to save Sora, his best friend's original self, who stayed with him until the moment he faded. He sincerely apologized to Sora for getting Kairi involved. Confused, Sora asked him what he was trying to do and Axel confessed that he wanted to see Roxas, the only one who made him feel like he had a heart. Oddly enough for Axel, Sora made him feel the same way (possibly since Sora and Roxas are one and the same) and used these final words to urge Sora on to rescue Kairi. Axel opened the passageway to the World That Never Was with the last bit of strength he had in him before disappearing into darkness completely.
Afterward, Xigbar and Luxord were curious about Axel's foolish and senseless actions; essentially turning against the Organization for the sake of his friendship with Roxas, but Xemnas revealed that Axel's disappearance served to stir Roxas from his rest, claiming Axel's disobedience was not entirely meaningless and pitiful. Xemnas also stated that due to contact with Sora's heart, Axel's own ability to feel emotions could have been affected. Naminé, however, backs up this notion in the written novel of the game in which she mentions that Axel never truly died, but rather faded into darkness where he would wander until he would find his heart. Axel made one final appearance to Roxas, right before the latter's mental battle with Sora, where he gives a final farewell to his best friend.
Kingdom Hearts CodedEdit
In the Data Castle Oblivion Episode 8, the data Naminé reveals to Data Sora and King Mickey that Axel is one of the people that, while gone, is still connected to Sora's heart.
Axel, Roxas, and Xion are seen in the secret ending of Kingdom Hearts Birth by Sleep, Blank Points, sitting happily together on the Clock Tower with sea-salt ice cream. The trio look into the sunset and Roxas and Xion say Sora's name.