Cocona is Croix Bartel's adopted little sister. She gets along with him quite well (lovingly calling him him "Cro") though thay are not related by blood, she is actually a Reyvateil herself, but she has not yet matured and is unable to use Song Magic fully. However, she is able to craft a little fireball in combat, showing that she can at least command the most basic Song Magic that all Reyvateils can use. She fights using a special hair ornament, which can turn into a double-bladed baton. This weapon idea was originally created by Croix for her.
2 years prior, during a particularly bad IPD outbreak where she lost her real family, Croix approached her, asking her if she was hungry. Thus, he adopted her and they've lived together ever since. During that outbreak, she also witnessed the Maiden Cloche leading the knights in order to help protect the slums and even cry as she held a baby she was unable to save. This made Cocona see Cloche in a new light, and she found herself deeply respecting her. She trained herself to become physically strong enough to support Croix in battle, until the point in which she was admitted into the Grand Bell Knights, with the position of a Satellite Girl.
During the time she spent living as Croix's adopted sister, they got along pretty well, but they also fought many times, frequently over very trivial stuff. The most peculiar of these episodes was when Croix accidentally used a Gergorilla toothbrush of Cocona's, which was very treasured by her due to its massive rarity among the Gergo merchandise, and ended breaking it up. Cocona got so enraged at him that she didn't talk to him during all the day, and she only forgave him because of all the efforts that Croix made to buy a new toothbrush like it for her. However, these efforts were fruitless, and Croix could only give her a Gergo piggybank she wanted, since all of the limited edition items that were being given at the Fancy Shop that day, including the toothbrush, were sold out before they finished paying the piggybank. Cocona still harbors some rage at Croix due to this.
Events of Ar tonelico II: Melody of Metafalica
At the start of Ar tonelico II, Cocona was waiting for Croix in Pastalia, and berated him for being late from a mission. They talked a little about the dreams that Croix had about Metafalica, and his disappointment about the Knights only performing IPD Containment missions all the time. After this, they began doing some shopping in preparation for the next day, in which Luca would come to stay with them. At the weapon shop, Cynthia gave her the protectors she had ordered, and got some laughs out from the way in which Cynthia was teasing Croix.
However, when they returned home, Croix was called by Captain Leglius because an emergency had took place: the Rakshek Resort, in which Lady Cloche was spending her vacation, had been made the target of an IPD outbreak. Cocona was allowed to join Croix for this mission, although Croix had to remind her that they weren't going to play. Cocona also pointed the fact that if she was a Reyvateil, she and Croix would be much more powerful than anyone because of how closely bonded they were, although Croix just told her to brush off these thoughts from her head. Once they came into the Resort, they were attacked by blue-armored knights, which made them to realize that the outbreak was nothing more than a coup d'état perpetrated by the Sacred Army. They managed to reach and save Lady Cloche, but were forced to flee to the nearest town of Rakshek, where Luca worked as a Dive Therapist. In here was that Cocona met with Luca for the first time, after hearing so much about her from Croix.
It was decided that they would hide out with Luca while they reunited with Leglius, and until they found a way to return to Pastalia. After they reunited with Leglius, Cocona seemed somewhat strange, although she replied that she was simply tired. This was no more than an small foreshadowing of the events that would come soon.
After they returned from Enna to Mint Block with Luca at their side, Cloche's health suddenly took a turn for the worse, and since they couldn't ask for help from Pastalia because of the Grand Bell being under attack by the Sacred Army, they had no choice but to head out and march through the Ironplate Desert, in search for a way to return to Pastalia.
However, during a brief rest they took while walking through the desert, Cocona herself was then revealed to be an IPD-Infected Reyvateil, and furthemore, a Level 7 one, displaying symptoms which result in her being taken away and contained in the IPD Labs, where they presumably experimented on her. Croix tried to keep the knights from taking her away, but he was beaten until he was almost dead, and Amarie has to intervene to avoid him getting killed. Later on, she was rescued from the Labs by Croix and the others, although a little later all of them were thrown in the jail. Cocona was the first one to be freed, thanks to the trust that Croix had in her, and the fact that Cloche managed to arrange things so their intrusion in the Labs would be just considered as a simple training accident. She also follows Croix despite the decisions he would make regards to protecting Cloche or Luca.
However, it's only in Cloche's path that Cocona learns that both of them are large Gergo fans, and even shared with Cloche the small incident in which Croix accidentally used a limited edition toothbrush, which caused Cocona to get pretty angry on him.
In both paths, after the creation of the false Metafalica and the temporary death of one of the Maidens, Cocona and the group returned to Pastalia to confront Alfman. Since Leglius forbid Amarie from entering Grand Bell, Cocona volunteers to scort Amarie back to the house she shared with Croix. However, the two of them end up chasing Chester as he went into the Lakra system where it's discovered how the IPD Reyvateils are connected to each other, as Cocona begins to say the same things as Lakra simultaneously and without her knowledge.
During their exploration of Gaea, she also expressed her opinions about how Jacqli was so "boo" due to wanting to obtain the Heart of Gaea at any costs, no matter if this meant the death of the Maiden who got turned into the land. However, when Jacqli joined their group later on, she befriended her, and began asking all sorts of questions about the machines that they found in the Dreamy Fields Underground. Cocona was also the first one to notice the secret stairwell in the Cat Mansion that allowed them to find Jacqli's hideout.
Due to her being an IPD, she was also affected when EXEC_HIBERNATION/. is sung to shut down Infel Phira, collapsing and saying it feels as if her body has no power. Upon learning this, Jacqli immediately supposed that the song was being used to hack into Infel Phira and reformat it, thus deleting the Cosmospheres of the IPDs. This fact was illustrated when, upon taking Cocona away from the Hill of Metafalica in search of a method to save her, she became weaker, and started gradually losing her memories.
After unsuccessfully trying to stop the singing of Hibernation at Lakra, Jacqli proposes that since Infel Phira is being hacked, they could enter Cocona's Cosmosphere to make an entrance to Infel Phira's Binary Field by destroying her her Boundary Gate, which would allow them to stop the reformatting. Since Cocona was still an immature Reyvateil, such a feat was possible, however it could cause the collapse of her mind and fatal damage to both Cocona and Croix. Croix at first refused to do such a thing to Cocona, but after Cocona asked him to do it, and that she wouldn't mind if she was killed if Croix was the one to perform this act, Croix initiated the Dive. Once Croix entered her Cosmosphere, he found himself in a vortex of multiple colors and physical sensations, unable to form a concrete world. There, he met up with Cocona, who expressed to him the worries she has for the future, and the shared sadness and anxiety that the IPDs have felt during centuries. Despite this, and the fact that she doesn't even remember Croix at this point, his feelings reach and resonate with her, and she allows him to break her gate, thus allowing them to stop the Ascension Plan.
She miraculously survived this act, but fell into a coma together with the other IPDs. While Jacqli herself doubted about whether or not she could return to normal after getting her Boundary Gate destroyed, she later awakens with the rest of the IPDs when Cloche sings METHOD_IMPLANTA/., completely safe and unharmed.
After Cloche retakes control of the government, she is seen encouraging Cloche as she heads to make her first speech since she became hated by the public for failing to produce Metafalica.
After the final battle, and having gone with the party throughout all of Metafalss to hear the feelings that would give shape to Metafalica, she and Croix returned by themselves to their home. In there, Cocona told Croix about how they didn't talk in that way since their adventure started, and about how excited they were to see Metafalica's completion.
In all of the endings, she is called by Jacqli to come with her to where the Heart of Gaea of Metafalica lies, and upon extracting an small piece from it, she explains to Cocona why the planet of Ar Ciel is in such a deplorable state, and asks her to go to Sol Cluster, to the Tower of Tyria, and give that fragment of the Heart to an acquaintance of Jacqli, Harvestasha. She asks this from Cocona because she is an IPD, and furthermore, despite being a Reyvateil, having an excellent physical prowess, which would allow her to be accepted by the Reyvateil community of Clustania, and if anything happened, her abilities would allow her to get out of any situation.
In her own ending this is further expanded to where she tells Croix about her journey, and despite Croix initially forbidding her from going, he finally allows her to go, and after hugging, Cocona tells him that she will return to his side, no matter how many years it will take her to accomplish her mission.
Events Between Ar tonelico II and Ar tonelico Qoga
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Cocona goes with Sasha to Sol Cluster to meet Harvastasha. However because Cocona is an IPD Reyvateil who depends on the Infel Pira for her Song Magic, the Clustanian Reyvateils are unable to identify her, instead perceiving her as a threat and attack Cocona and others. She is injured in the attack and is found by Reverand Gengai, who takes her to his acquaintance Dr. Hikari Gojo who happens to be a Reyvatologist. After being treated, Cocona decides that since the Clustanian Army is still on the look-out for her, she might be safer in a disguise.
Events of Ar tonelico Qoga: Knell of Ar Ciel
Main article: Tatsumi
In the form of Tatsumi, she is asked by Finnel if she carries the Heart of Gaia. They agree together to travel with Aoto to the Tower in order to meet Harvestasha.
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- She is the only Reyvateil fighting in the frontlines rather than being protected in the game series. (Until AR III)
- Her age given in the US version of Ar tonelico Qoga is 16, due to localization concerns and to avoid potential problems with her portrayal in the game. However, it could be excused as a simple lie to make herself appear older than what she actually is.
- In the original game, she had the habit of speaking in third person when referring to herself (can be heard also during JP voice acting). However, this detail was lost in all translations.