Rika Shiraki holds the position of student council president at her academy. Her affluent and influential family background grants her an untouchable status among students. She enjoys widespread popularity, particularly with male students, due to her attractive appearance, charm, and approachable demeanor. She forms a romantic attachment to Taki Minase, the protagonist. This affection arises naturally in certain narratives, while in others, it stems from Minase's use of a love spell from the "Bible Black" book. Notably, an attempt to manipulate her feelings using the "Paper Doll Charm" spell fails because her genuine emotions for Minase already exist, making artificial influence redundant.

Her narrative role and experiences differ significantly across adaptations. In the anime, she becomes involved in the central conflict after uncovering Minase's connection to Hiroko Takashiro. This culminates in her stabbing Minase in a crime of passion, engaging in sexual activity with him as he bleeds, and intending to kill him before Takashiro intervenes to save him. Conversely, the visual novel's "Lawful Route" reduces her significance to the main plot, as Minase refrains from using magic on her. Within the game's continuity, she shares narrative functions and specific scenes, including those depicting violent revenge against Minase, with another character named Ito.

She reappears in the sequel series "New Testament," set years later, now working as a substitute teacher at the same academy and striving for a permanent position. Despite enduring past trauma involving supernatural manipulation and assault, she retains a warm and open-hearted nature. She maintains contact with Hiroko Takashiro, now a nun, and exhibits either forgiveness or a lack of memory regarding past harmful actions by Kaori Saeki against her. Though no longer a virgin, she remains a target for antagonists; Saeki's henchmen drug and abduct her for implied unpleasant purposes related to ongoing rituals.

Personality assessments describe her as understanding and extroverted. She balances loyalty to friends and institutions with a strong sense of responsibility, driving her involvement in activities like the school newspaper. Beneath her resilience lies vulnerability; she struggles with self-loathing and denial, masking her need for support by projecting self-sufficiency and assuming others possess similar strength. Contradictory traits include a playful sense of humor alongside serious dedication to her duties and a fondness for cute aesthetics, excluding food-related contexts. Some analyses suggest MBTI classifications such as INFP or ENFJ, emphasizing her empathetic nature and complex inner conflicts.