Hitsuji no Uta

Kazuna's family is plagued by a genetic disorder causing an uncontrollable craving for blood, similar to vampirism. He was adopted by the Eda couple as a child and remained unaware of this legacy until the symptoms began to manifest in him. His older sister, Chizuna, who has endured the condition since childhood, attempts to help him manage his impulses and minimize the burden associated with the disease.