Juliet Fiammata Asto Capulet, who also goes by the names Odin and the Red Whirlwind, is the sole surviving member of the Capulet family and the female protagonist of the story. As a two-year-old child, she was the only one to escape a bloody coup led by the Montague family that slaughtered the rest of her house and seized control of the floating city of Neo Verona. She was rescued by a loyal family retainer named Conrad, who raised her in secret along with a small group of other Capulet loyalists hiding beneath a theater.

To protect her from the Montagues, who continue to hunt for any remaining Capulet heirs, Juliet is forced to conceal her true gender and identity by dressing as a young boy named Odin. Despite the constant need for secrecy, her inherent sense of justice and compassion for the oppressed people of Neo Verona compels her to take on a third persona, that of a vigilante known as the Red Whirlwind. In this guise, she uses her exceptional skill as a swordsman to fight against the tyrannical rule of Lord Montague and aid those who are suffering.

By nature, Juliet is portrayed as a kind, strong-willed, and pacifistic young woman. She possesses a deep love for her friends and a strong sense of duty, though she initially chafes at the restrictions of her life, particularly being forced to live as a boy. She has a tomboyish personality but also embraces the rare opportunities she gets to express her femininity. On her sixteenth birthday, Conrad reveals the truth of her heritage to her, and after a period of internal conflict, she begins to accept her role as the leader of the Capulet rebellion against the Montagues. Initially, she claims to have no desire for revenge, but after witnessing the death of a fellow rebel, her resolve hardens, leading her to discard her male disguise and openly lead her followers in a fight for freedom.

The central conflict of her life arises when she falls in love with Romeo Candore Van de Montague, the idealistic and kind-hearted son of her family's mortal enemy. They first meet at the Montague Rose Ball, where Juliet, dressed as herself for the first time in years, shares an immediate and powerful connection with Romeo. When she learns his true lineage, she is torn between her growing feelings for him and her responsibility to lead the rebellion against his family. She tries several times to distance herself from him, but their love proves too strong, and they eventually pledge themselves to each other, fleeing their responsibilities for a brief period of peace. Her relationship with Romeo forces her to constantly re-evaluate her motivations, shifting her focus from personal vengeance to a vow to create a peaceful future for Neo Verona alongside him, and she ultimately comes to see the Montagues not just as enemies but as a family she could belong to.

Throughout the story, Juliet undergoes significant development. She transitions from a girl with no memory of her past who simply follows the orders of her guardians into a decisive leader and a symbol of hope for the people. She is often conflicted, struggling between her peaceful nature and the violent path of rebellion, but her love for Romeo and her desire for justice guide her actions. A key part of her development is her dual role as a skilled but reluctant warrior. As the Red Whirlwind, she is a capable and agile fighter, but she is deeply affected by the act of killing, showing her compassionate core. Her most notable ability is her swordsmanship, which allows her to fight on equal footing with the best knights of Neo Verona. Later in the series, she learns of a dark secret: the floating city of Neo Verona is held aloft by a divine tree called Escalus, which requires a sacrifice from the Capulet bloodline to survive. Accepting this as her ultimate duty, she willingly offers herself to the tree, making a heroic sacrifice to save the land and people she loves, believing it will reunite her with Romeo.