Prince Cayenne is a mysterious prince candidate in Jewel Land. His appearance uncannily resembles Momona's older Earth cousin, but their personalities diverge. He sports tousled navy locks and topaz eyes, typically dressed in layered attire: a white dress shirt, red hoodie, and a black-grey-white blazer with golden buttons, brown dress pants, and loafers.

Orphaned, Cayenne is driven by his resolve to protect his home and become a pillar supporting the Lady Jewel. Early on, he denies but is later exposed as having a secret relationship with Lillian, whom false memories—implanted by the antagonist Joker—led him to believe was his adoptive younger sister. When revealed that Lillian was originally Lady Diana's magic-animated doll, Cayenne chooses to continue treating her as his sister, vowing to restore her humanity.

His personality balances princely grace with a tendency for playful teasing and challenging beliefs. Though occasionally cool, his actions remain consistently kind. He develops romantic feelings for fellow protagonist Momona, culminating in a kiss during a hot dog stand date. Complications arise when Cayenne is selected for study at the Royal Palace, physically separating them but sustaining their bond through messages.

Cayenne faces significant tasks and trials. He prioritizes Momona's rescue over a critical duty, yet still earns recognition. Later, he pushes himself excessively to qualify for Royal Palace candidacy alongside rivals Romeo and Soarer, resulting in a fever that makes him miss a meeting with Momona. His eventual Royal Palace selection deepens his emotional commitment; he confesses his love to Momona before departing.

Demonstrating loyalty and growth, Cayenne reconciles his protective bond with Lillian and his love for Momona. After both temporarily lose and regain memories during a crisis threatening Jewel Land, he marries Momona. This marriage cements his role as a stabilizing figure within the realm's hierarchy.