Claire Kagenou/Chronology

Training and Youth
Claire was born to Mr. and Mrs. Kagenō of the Kagenō Baron Family, and always wanted a baby brother until she finally got Cid. During her childhood, Claire was trained in swordsmanship and magic in order to continue on the family name, surpassing her brother in performance and academics.

At age 8, she dragged her brother into the forest for special training, but have encountered the Scarface Gang. Wanting to protect her brother, begged him to flee while she fought off the members of the scarface gang, but to her horror she see's Cid come to her defense and get knocked out just before she passes out. She would later wake up to find her brother alright and see's that the members of the Scarface Gang missing, she was told that a band of hunters chase away the bandits away, however unbeknownst to her that it was Cid that kill all the members of the Scarface gang.

At age 12, Claire often trained with her younger brother Cid outside their house, but was unfortunately disappointed in his underwhelming performance and berated him for it before choosing to punish him. Despite this, she still sought to practice with him whenever possible as she would refine her skills better than with anyone else, and hoped to teach Cid to be better.

Claire learned that she contracted the Demon Possession when she reached age 14. Fearful that she may not live long, she dedicated much of her time with Cid and prepared him for the future. Unbeknownst to her, Cid had secretly cured her while doing "strencthes", and she continued on watching out for him.

Kidnapping & Rescue
When Claire already become 15, she was ready to leave to the capital of Midgar Kingdom and attend the Midgar Royal Spellsword Academy. The night before her departure, the Cult of Diablos infiltrated her family home and kidnapped her with the purpose of using her for their experiments.

Claire was held inside a dungeon where she learned that her kidnapper was Viscount Grease. After delivering some cruel comments about him, Grease inquired if she had suffered Demonic Possession, to which she vaguely confirmed and accidentally brought up Cid during their conversation, causing Viscount Grease to decide to bring him in as well for questioning. Enraged at this admission, Claire broke free of her chains and attacked the Viscount, only to have him knock her unconsciousness. Unbeknownst to her, she was rescued by Cid and his Shadow Garden, and she returned home safely by her own power.

Novel/Manga
Claire hurriedly confronted Iris Midgar after learning that her brother was suspected of kidnapping Iris's sister, Alexia Midgar. She knew that whether or not Cid was a suspect, this would ultimately lead to his execution, and tried vouching that her brother was innocent. This did not move Iris, causing Claire to nearly assault her but was dragged out by Zenon Griffey before that could happen.

Anime
After hearing that her brother was a suspect for the kidnapping of Alexia, although she was told to stay in her dorm wanting to save her brother she left her dorm room wanting to speak with the knights and explain that her brother couldn't have kidnapped anyone. However she was stopped by the other students trying to stop her, Claire had also knocked out two of the students that were trying to stop her. When Rose tried stopped her, and Claire had assaulted her and later was subdue by her. Claire would also dislocate Rose's shoulder still trying to go save Cid but was stopped by the others students. After hearing the knights had cause harm to her brother, Claire wanted to give the knights what they deserved for hurting him but was stopped by Rose and the other students would force Claire back to her dorm.

Sanctuary Infiltration
In the anime, Claire would stop by at Cid's dorm to search for him to go back home for summer vacation with him, which is earlier due to half of the academy being destroyed. But, Claire was unable to find him due to him hiding above her on the ceiling and had left to go home alone for summer vacation.

Bushin Festival Tournament
When the Bushin Festival began, Claire became her school's representative after the previous representative, Rose Oriana, became a fugitive and was disqualified. Claire went to Cid's room to invite him to see her matches, but much to her anger, he was gone. She eventually found her brother and throttled him for making her wait at his dorm, before she explained to Cid and offered him a ticket to a special seating at the tournament.

On the semifinal tournament, Claire's match has started and she wins the fight hoping Cid will watch her match. In the anime, during Iris's match against Mundane Mann, she went to the VIP lounge to find Cid but only to find him missing. Causing her to leave the stadium go search for him in the city. While searching for him she was unware of his battle as Shadow against Iris and Beatrix all over the capital.

At the tournament's climax, despite the several incidents that had occurred, Claire ultimately won the victory of the Bushin tournament by default.

Red Moon Incident
After winning the Bushin Festival, Claire was treated to dinner at Mitsugoshi Co's restaurants by Cid, where she expressed disappointment at Cid for falling behind his studies and not thinking enough about his future. So Claire proposed to her brother that she was going to take him to Lawless City to take part in the assault during the Red Moon event in hope to gain some credit and secure a better position for him.

Once they arrived, Claire left Cid alone while she attended a meeting between swordsmen at the Magic Swordsmen Association to form a plan to subjugate the Red Tower, and discovered that her brother was missing upon her return. She headed out to Outlaw City to search for him and encountered the Vampire Hunter, Milia, who informed Claire that her brother might have been taken to Red Tower to be sacrificed. Because their goals aligned, the two agreed to work together to stop the vampire queen's revival.

Using a tunnel to bypass the Vampires and Ghouls, Claire and Milia met Beta from Shadow Garden, who were there to get a sample of the progenitor's blood due to similarities with Demon Possession. Claire asked Beta if there was a way to cure Demon Possession for which Beta did not clarify but informed the former not to worry about it, much to Claire's confusion. The two then encountered Juggernaut who decided to kill them and nearly overwhelmed them until Milia was forced to reveal her secret to Claire, becoming a full-fledged Vampire to defeat their enemy.

But, Juggernaut was defeated by Shadow as he launches a fast casual upward kick, which the blow sends him flying until he smashes through the wall that leads outside of the tower and cursing Shadow. Claire saw Shadow, but she feels like she knows him but she never met him until Shadow left. When Milia asked about her situation, Claire replied that she was fine and wanted to give an explanation about who she really was and Milia revealed to Claire that she was a Vampire then told her past as a follower of the Blood Queen. After telling her story, Claire doesn't care about her true origins and decides to save her brother together

Eventually, the two finally reached the tower where Claire was relieved her brother wasn't the sacrifice and that Elisabeth was finally resurrected. Claire was impaled before the Vampire Queen grabbed her and sucked her blood, allowing Elizabeth to regain full power. Thankfully, Claire was saved by the spirit of Aurora, who temporarily took over her body and unlocked her full abilities to combat Elizabeth. This fight held the Vampire Queen long enough for Shadow to finish it.

After the battle, Claire reunited with Cid and the two siblings leave Outlaw City, but not before saying goodbye to their vampire friends.

The Academy Disappearances
As the Cult began abducting students, Claire was among those taken and readied for an experiment to merge with the other arm of the demon, Diabolos. After Shadow and Zeta defeated the Fenrir Sect carrying out this villainy, and as Claire was already Aurora's host, Zeta followed her own scheme to immortalize her master Shadow and forcibly bonded Claire to the demon arm.