Juliet Fiamatta Asto Capulet is the last member of the Capulet family. She masquerades as a boy, Odin, in order to avoid being caught by the usurping House of Montague, who still actively look for the Capulets. An excellent swordsman, she also masquerades as a vigilante, the Red Whirlwind, in order to aid the people oppressed by the rival Montagues. Initially, Juliet has no recollection of her troubled past and chafes at being forced to dress as a boy. The truth of her heritage is revealed to her by Conrad on her sixteenth birthday. Her memories of the fateful night 14 years ago float to the surface soon after she unsheathes the Capulet Ghat. Even so, Juliet at first claims that she has no desire for revenge. But after witnessing the death of a Red Whirlwind ally, Lancelot, she steels her resolve for vengeance. She discards her male disguise and leads a rebellion of Capulet loyalists against Montague. She is pacifistic and kind by nature, and tries to find alternative solutions to conflicts other than killing or violence.

She is often torn between her responsibilities as the last Capulet and her love for Romeo. She falls in love with him at their brief meeting at the Montague Rose Ball, only managing to introduce herself when they meet again in a field of irises. When she learns Romeo is from the Montague family, she tries unsuccessfully to distance herself from him. They eventually escape from their responsibilities and pledge themselves to each other in an abandoned temple, living in peace for a time. They were captured by Montague pursuers and taken back to Neo Verona, where Juliet was imprisoned as a criminal. Before she escaped with her allies, Romeo promises to make a future a future of peace. Since this time, she considers Lord Montague as her family and only fights to bring peace to Neo Verona, as her part of her vow with Romeo. She is well-liked by the people and they eventually join her in rebellion Monatague.

Late in the series, Juliet discovers from Ophelia that her Capulet heritage is needed to sustain the Great Tree Escalus, a divine tree that supports Neo Verona. She accepts her duty to become the tree's sacrifice but solely tells Tybalt of her fate. After Lord Montague's death, she is forcefully swept by Ophelia to Escalus. Though her comrades and Romeo save her from Ophelia, Romeo is mortally wounded from the struggle. Determined to save her home and to uphold her promise to him, she voluntarily sacrifices herself, believing that they will be together for eternity.