Caren Hortensia appears in the second season of the anime Fate/kaleid liner Prisma Illya, known as 2wei!, as a member of the Church. Her public-facing role is that of the school nurse at the elementary school attended by the protagonist, Illyasviel von Einzbern, though her true purpose is to serve as an agent dispatched by the Church to observe the operation to recover the Class Cards. She is also acquainted with Illya's mother, Irisviel, suggesting a prior history.

In terms of background, Caren is the daughter of Kirei Kotomine and Claudia Hortensia. Following her mother's death, she was raised by her mother's relatives, taking their surname, and was brought up within the Church, eventually becoming a priestess herself. She has light grey hair and golden eyes, traits inherited from her mother, and is often seen wearing bandages due to her unique constitution rather than for aesthetic reasons.

Caren possesses a deeply complex and contradictory personality. On one hand, she can exhibit an angelic and forgiving demeanor, appearing devoted to helping others. On the other hand, she has a pronounced sadistic streak and derives genuine enjoyment from exploiting the emotional vulnerabilities of those around her, often making troubling statements with a calm and detached expression. She is a figure who seems to exist in a state of perpetual boredom, finding amusement in the chaos and distress of others. Despite her cruel tendencies, she is not a villain; she accepts her own twisted personality without shame or regret, viewing it as an inherent part of who she is.

Her motivations are tied to this nature and her duties. While she carries out her mission for the Church, including serving as a demon-detecting radar, she is also driven by a personal curiosity about pain and suffering. This is reflected in her decision to forgo a skirt on her combat exorcist uniform, a choice she claims is for mobility but also admits is intended to provoke and seduce, aligning with her calculated and provocative approach to the world. Her role in the story is that of a mysterious supporting character who observes the main cast from the periphery, often offering cryptic comments that hint at her deeper knowledge of supernatural events. She does not typically engage in direct combat, viewing her primary function as a living detector for demonic activity.

Regarding key relationships, Caren has a notable connection to Irisviel. She also works in conjunction with Bazett Fraga McRemitz, serving as backup for the Class Card recovery mission, though her relationship with the main trio is largely observational. She seems particularly interested in Kuro, whom she refers to as a miracle. In terms of development within Prisma Illya 2wei!, Caren remains a relatively static character, arriving as an enigmatic and morally ambiguous figure and fulfilling her function as an observer without undergoing a significant personal transformation. Her presence adds a layer of complexity and intrigue, providing a link to the wider operations of the Church.

Her notable abilities are distinct and tied to her nature. Caren possesses a rare genetic condition known as Masochistic Spiritualistic Automatism Diathesis. This constitution causes her to take on the physical injuries and spiritual afflictions of anyone nearby who is possessed by a demon or evil spirit, effectively turning her into a living radar for supernatural threats, which explains why her body is constantly covered in bandages. For combat, she wields a Holy Shroud known as the Shroud of Magdalene, a red cloth that is a conceptual weapon with the property of being able to bind any male, regardless of strength, though it has no offensive capabilities of its own and its binding effect is nullified if the target is attacked from the outside.