Hitsuji no Uta - S01

Kazuna comes from a family cursed with a disease that causes an uncontrollable, vampire-like craving for blood. Unaware of this legacy, he was sent away as a child to live with the Eda family. Now, as the sickness starts to manifest in him, he meets his older sister, Chizuna, who has struggled with it since she was young. Understanding the heavy toll it takes, Chizuna tries to guide him, helping him manage his urges-but the path ahead isn't easy.