A genetic curse that masquerades as disease, passed down through blood like inheritance itself. Kazuna and Chizuna don't fight their condition, they carry it, together, in the unbearable quiet between episodes. The show moves slow enough that you feel the weight they're feeling, and four episodes somehow contain the entire architecture of a family tragedy.

Kazuna was sent as a child to live with the Eda couple, unaware that his family has a history of a disease that causes an uncontrollable, vampire-like thirst for blood. When signs of the sickness begin to appear in him, he comes into contact with his older sister, Chizuna, who has suffered from it since early childhood. Knowing how heavily the illness weighs on those who carry it, Chizuna tries to lighten her brother's burden and help him learn to control his urges. The four-episode OVA is a drama with horror elements.