Kyoukai no Kanata S01

Mirai Kuriyama is the sole survivor of a clan of spirit warriors who have the ability to use their blood as a weapon. As such, Mirai is tasked with hunting down and killing "Yomu" - creatures said to be born from human negative emotions. One day, while Mirai is lost in thought on the school rooftop, she encounters Akihito Kanbara, a half-Yomu in human form. Frightened, Mirai turns her blood into a weapon and enters Akihito's body, only to discover that he is immortal. From then on, the two become friends, but Mirai still tries to kill him. Gradually, Akihito convinces her to join the school's literature club, where two other powerful spirit warriors are also members.