The leader of the 1st Year High School division of the "White Cats". She is the only daughter of the Persia household, a high ranking noble family from the West. Since only males can inherit the rank of nobility, the household is at risk of losing its noble status. This motivates Juliet to become stronger so that her strength and intelligence are no less than that of a man. She initially mistakes Romio's protection of her as pity for being a woman and has been harboring animosity towards him until he confessed his love.
Throughout the series, her feelings towards Romio grow, to the point when she can confidently express her love for him in front of others. Her cooking skill also grows, although she can currently only bake cookies. When going out with Romio publicly, she goes undercover as a "Black Dog" Middle School boy named Julio.