Jessica Valentine is a student at the Ansullivan Dragonar Academy, where she is in the same advanced grade as the protagonist, Ash Blake. She initially serves as the president of the Silver Knight Fan Club, also known as the SKFC, an organization dedicated to the mysterious hero known as the Silver Knight. Her public persona is that of a self-assured young lady from a noble family, but this is a fabrication. Jessica comes from a common background; her father is a butler employed by the Randall family, and her act of nobility is fueled by a common girl's aspiration to elevate her status, potentially through a favorable marriage.

Personality-wise, Jessica is bold, energetic, and remarkably persistent. In her early appearances, her single-minded devotion to the Silver Knight leads her to make shocking public declarations, such as her desire to bear the Silver Knight's child, an ambition she pursues with startling directness. This behavior initially paints her as an opportunistic social climber. However, her character proves to have more depth. During a crisis when the cathedral is attacked, she bravely volunteers as a hostage in an attempt to save others. Despite being humiliated and left in a vulnerable state, she displays genuine courage and refuses to show weakness. This pivotal event changes her motivations entirely. After being rescued by Ash Blake, who is revealed to be the Silver Knight, her infatuation shifts from the mythical hero to the person who saved her life, leading her to pursue Ash himself with the same relentless passion.

Her role in the story evolves from a comedic antagonist to a firm ally. After learning Ash's secret, she is brought into the student council by its president, Rebecca Randall, to ensure her silence. She later becomes a key member of the Avalon Holy Dragon Knights, a group formed to support Ash in larger conflicts. Her key relationships include her childhood friendship with Rebecca, who knows the truth about her commoner background and often keeps her antics in check. Her primary partnership is with her dragon, Rhiannon, a water dragon. Through their bond and dedicated training, Jessica achieves the rank of an Arc Dragoner, a significant evolution that grants her a unique trident as her signature equipment.

Throughout the narrative, Jessica remains a passionate and comedic presence, frequently and openly competing with other female characters for Ash's affection. She undergoes clear development from a pretentious noble wannabe to a courageous and loyal knight, proving her bravery in battle and her commitment to her friends. Her persistence and academic talent are also notable, as she is a skilled enough student to qualify for competitive training camps.