Thirty-five years prior to current events, Nea, in order to become the new patriarch of the Noah Family, attempted to stop the Family and the Millennium Earl's plan to wipe out humanity. He succeeded in killing all the Noahs except Road and the Millennium Earl. During this time, he also locked the location of the Ark above Edo, making it impossible for the other Noah to change its location, although it remained otherwise functional. Eventually, he went on the run, attempting to keep his brother, Mana, safe and ensuring his eventual reincarnation should he die. He requested that Cross Marian watch over Mana, promising that one day he would return from the dead. Nea was eventually killed by the Earl, driving Mana insane and leading Cross to begin to search for his reincarnated form. Some twenty years later, he was reincarnated within Allen Walker, his adopted nephew.
Initially, Nea simply appeared to Allen as a shadowed figure with no distinct facial features wearing a large overcoat. Once, he appeared briefly to the Earl in his mind as a young man with unruly, darkly-colored hair. In his Noah form, Nea appears as a young man with short, unruly dark hair with a line of stigmata on his forehead, wearing a dress shirt, vest, a simple cravat, and an overcoat and white gloves. His facial features have been noted by both Wisely and Allen as making him strikingly similar in appearance to Tyki Mikk, though Tyki has more mature facial features and Nea's hair is shorter and he lacks Tyki's facial mole.
Not much is known about Nea's personality. He often speaks gently to Allen in their encounters, and seems to mean him no harm, despite the fact that he will consume Allen's body and be reborn. It is also apparent that Nea's will is to gain revenge against the Millennium Earl upon his rebirth. No motive has been given as to why Nea betrayed the Earl, though Cross Marian implies in his conversation with Allen Walker that Nea discovered a third side to the war between the Noah Family and the Black Order.
He was, however, very close to his brother, Mana. Road claims that Nea fought on behalf of his brother. Wisely states that Nea experienced the fear of knowing that there is nowhere a Noah can run and hide from the other Noah 35 years ago.
Suman Dark's Fallen arc
Nea first appears to Allen. After Allen is nearly killed by Noah Tyki Mikk, he spends some time unconscious, wandering around in his mind in a vaguely sketched, child-like form on a small, paved island in the middle of a body of water flanked with skeletal trees, with a white moon above and a black reflection of the same moon in the water. When Allen looks down into the water and sees the European Branch in shambles within it, Lenalee sitting on the rubble with his body draped across her lap as she cries, Allen reaches out for her, only for a hand to emerge from the water and take his. His form solidified, Allen tries to pull away from the hand, watching as the surface of the lake freezes over, demanding that the hand let him go. The ice cracks, a shadowed form (Nea, though this is unknown to Allen at the time) tells him no, and immediately after Allen awakens.
Noah's Ark arc
Nea's "Fourteenth" shadow form. Because of Nea's actions thirty-five years before, Noah's Ark, which the Noah Family has been using for years, is locked in place above Edo, Japan. Road and the Earl attempt to start a 'download' of the old Ark's information to make a new one, but Cross Marian intervenes at the last moment and sends Allen Walker into a special, white room within the crumbling Ark where a piano sits. Nea tells Allen how to control the Ark. There, Allen sees the shadow of the Fourteenth again, the Fourteenth speaking to him this time and telling him he can use "his" Timcanpy and the piano, which the Earl does not know of, to pilot the Ark. When Allen tries to ask the Fourteenth who he is, he does not receive an answer, Nea simply continuing to smile at him. As Allen begins to play, recognizing the crest and musical 'notes' Timcanpy is displaying for them, the Fourteenth explains that the notes are a song within Allen, encouraging Allen to "hope" to get the Ark to do what he wants it to. Invasion of the Black Order arc Edit Allen accepts the fact that Nea's shadow won't go away. After appearing in the Ark, Nea begins to appear in his "Fourteenth shadow" form in every reflective surface Allen encounters, throwing Allen off at first before he starts to accept his presence, rationalizing it by thinking of Nea's shadow as one of the human souls bound to an Akuma. Destruction of the Black Order arcEdit
While packing up the things within the European Branch and preparing to move to a new location, Allen reflects on whether or not Mana loved him or if the man was just using him, willingly looking at the Fourteenth's reflection in a mirror as he thinks about Mana telling him (Allen) that he loves him.
Disappearance of Cross Marian arc
Nea's old ally and Allen's master, Cross Marian, eventually chose to reveal that Allen is the host for Nea's rebirth and that he is the brother of Allen's adoptive father, Mana. This revelation ultimately resulted in Allen being placed under even stricter observation, with the Black Order preparing to execute him should Nea overtake his consciousness.
Phantom Thief G arc
The Fourteenth takes control of Allen's body. During battle, Allen deliberately impales both himself and a Level 4 Akuma with his Sword of Exorcism. Because the sword only harms evil things (namely Akuma and Noah), Allen believes that he will not be injured, but begins to cry out in agony as it attempts to exorcise the Noah memory within him. Nea awakens briefly, using the Akuma to call out to the Millennium Earl,but quickly falls back into Allen's subconscious after Yu Kanda calls Allen by a much-detested nickname, "beansprout".
Despite the fact that Kanda is obligated to report any signs of the 14th's awakening, Kanda does not mention the event to anyone and Allen remains unaware of his momentary lapse of control.
Third Exorcists arc
Nea after Allen's dream. While recovering from the injuries his Sword of Exorcism inflicted upon him, Allen has a dream of Mana, and when he awakens Nea is in control of his body. Nea retreats, though, when a nearby Lenalee Lee calls out to Allen, who saw the look on Allen's face but doesn't comment on it. Mystery of Kanda arcEdit
After Allen and Yu Kanda are abducted by the Noah Family and brought to the North American Branch, the Earl speaks to Nea, taunting him into appearing by asking about when Nea used the Level 4 to communicate with him. Nea takes over Allen's body and confirms that he did, indeed, use the Level 4 to call out to the Earl, saying that he wanted him to know that he was back and that he would be coming to kill the Earl so he could take over the title of the "Millennium Earl".
Later, when Kanda impales Allen with his Anti-Akuma Weapon, Mugen, the damaged caused by the Innocence forces Nea's Noah side to react to the pain and take over Allen's body once more. Nea talking to Allen.
While Allen is unconscious, Nea meets him in his mind, keeping Allen chained to an odd, throne-like chair with wings as he comments that the Earl has become a mad puppet of destruction. He then comments that Allen also became an insane puppet before introducing himself by name to Allen. Outside of the area, Timcanpy activates a spell that forces a barrier set up around the North American Branch to explode, which allows Allen's suppressed Pentacle Eye to activate and force Nea back yet again.
Seed of Destruction arc
Fearing that Nea will consume Allen's consciousness and accusing Allen of treason, Allen is imprisoned by the Black Order. During this time, Allen is barely conscious. Nea attempts once more to overtake Allen's mind, but the sudden presence of danger as posed by Apocryphos gives Allen the strength to push him back. Sensing that his 'brother' is in danger, the Millennium Earl sends Tyki and Road to protect Nea's host. Searching for A.W. arcEdit
As Allen is briefly reunited with Kanda and Johnny after three months, Allen flees from the arriving Akuma and after being mocked by Wisely and Tyki, Nea begins to resurface in Allen.