Axel (アクセル, Akuseru?), the "Flurry of Dancing Flames" (おどる火の風, Odoru Hi no Kaze?), is a Nobody introduced in Kingdom Hearts: Chain of Memories. His original self was named Lea (リア, Ria?), and used to be friends with Isa before he became Saïx.[40] The character is voiced by Keiji Fujiwara in the Japanese release of the games, while Quinton Flynn provided the voice for English releases.[11][13][23] Much like his original self, to an extent, Axel wishes to achieve his own ideal of immortality by having everyone he comes in contact with remember him, saying the phrase "Got it memorized?" on multiple occasions. Entrusted to deal with Organization traitors, Axel controls the Assassin Nobodies, and fights with a pair of "chakrams" called "Eternal Flames" (エターナルフレイム, Etānaru Fureimu?) (although the weapons are more like wind and fire wheels from their construction) and fire manipulation.[7] Tasked with showing Roxas the ropes, Axel befriends the boy as his interactions with both him and Sora eventually cause him to express actual emotions as a result.[41] Nomura designed Axel based on a similar concept as Reno from Final Fantasy VII; Nomura wanted to see what it would be like to have a similar character in a different role and world.[2]

While as Roxas' mentor in the first half of 358/2 Days, Axel is reassigned to Castle Oblivion during the events of Kingdom Hearts: Chain of Memories, pretending to join with Larxene and Marluxia in their plan to seize control of the Organization. To gain their trust, he kills Vexen when ordered by Marluxia.[31][33] He then derails the plans by setting Naminé free so she can reveal the truth about Sora's manipulated memories to him. Axel then confronts Marluxia to finish the job, only to be forced to fight Sora instead. After Sora defeats him, Axel states the existence of their relation before vanishing. Axel later enlists the aid of the Riku Replica to get rid of Zexion in Castle Oblivion's basement levels before he attempts to locate the Chamber of Wakening. When Axel returns, he and Roxas befriend Xion, the fourteenth member of the Organization who, unknown to them, is an imperfect replica of Sora created by Xemnas. Learning of the truth, Axel reluctantly hides it from Roxas as his friendship with Saïx ended overtime while being forced in hunting down Xion when she attempted to leave the Organization. Later letting Xion go, with Roxas leaving the Organization, Axel attempts to persuade him to stay mainly out of fear of what Xemnas and the others would do to him.[42] Soon after, a frustrated Axel goes after Xion, refusing to let her sacrifice herself as he captures her.

In Kingdom Hearts II, Axel attempts to rescue Roxas from Ansem the Wise's virtual Twilight Town. Despite being faced with lethal punishment, Axel decides to let him be after a brief fight. Axel later begins acting on his own and kidnaps Kairi to bait Sora to him. Because Axel's actions began to appear increasingly deluded and foolish to his former comrades, Saïx later takes Kairi from him under Xemnas's orders. Axel meets Sora, Donald, and Goofy at Hollow Bastion, informing them that Organization XIII has been using them to get hearts.[43] Axel later finds Sora in a pathway to the World That Never Was and chooses to fight the Nobodies with him. The numbers get overwhelming and Axel performs a suicide attack to save Sora, who stays with him until he dies. Fading away, Axel apologizes for kidnapping Kairi and asks Sora to rescue her.[44] When asked what he was trying to do, Axel admits he wanted to see Roxas, revealing the effect both Roxas and Sora had on him.[45] With the last of his strength, Axel opens an entrance to the World That Never Was. In Kingdom Hearts II Final Mix, Axel posthumously contacts Roxas's consciousness following the latter's battle with Sora, reflecting on old memories and sharing one final conversation on the mysteries of the heart with him before fading away; a teardrop is seen falling as the two former Nobodies disappear. In the secret ending of Kingdom Hearts Birth By Sleep, he appears at Twilight Town's clock tower, along with Roxas and Xion, with whom he smiles at the horizon while Roxas and Xion utter Sora's name, and in Kingdom Hearts coded, he is revealed to be one of those connected to Sora's heart that he, Sora, must save, due to his connections with Roxas, who is Sora's Nobody.