Ciel (Tsukihime)

Ciel is one of the five heroines of Tsukihime. Apparently she looks like a senior attending the same school as the main protagonist Shiki Tohno.

Background
Ciel (whose real first name is Elesia) was a normal individual born in France to a French father and an Oriental mother. However, unlike those around her, Elesia had a high magic potential, and it was this rare characteristic which ultimately put Michael Roa Valdamnjong inside her as his 17th host body after his 16th host body was killed without having chosen his next host body.

In the process, Ciel became a vampire and killed everyone in her village, the massacre only ending when Arcueid Brunestud arrived and killed her, part of her duty involving killing Roa whenever he reincarnates. However, unlike previous hosts, Ciel returned to life after Roa had moved on to a new host. The secret Vatican agency known as the Burial Agency arrived and captured her, and over the course of a month she was killed repeatedly by the Church, only to rise again on every occasion, a living paradox in that she was both Roa (in that she was a host for him) while Roa was also inhabiting another, making it impossible for her to permanently die until the paradox can be rectified with the death of Roa himself. Eventually, despite their usual views on sorcery, vampires, and the like, the Church decided to use her abilities as a member of the Burial Agency, her main desire and mission being the elimination of Roa to end her eternal existence.