Hitsuji no Uta - S01

Kazuna's family has a history of a disease that causes an uncontrollable, vampire-like thirst for blood. Kazuna knew nothing about this, and as a child he was sent to live with the Eda couple. When the sickness starts to show signs of being present in him, he comes into contact with his older sister, Chizuna, who has suffered from it since early childhood. Knowing that the sickness places a heavy weight on those who suffer from it, Chizuna tries to ease her brother's burden, to help him learn to control his urges, but...