Author Mitsuru Hasegawa delves into a mysterious case linked to rumored vampire entities called 'Biters.' His childhood friend Yuusei Annaka, also known as Anna, cautions him against nosing around in dangerous matters. Little does he know, Anna is one of the Biters he's investigating. In a risky move disguised as research for his writing, Mitsuru consents to Anna feeding on his blood. Their encounter escalates as he succumbs to temptation and shares an intimate moment with Anna, uncovering a euphoric sensation. Moreover, a hidden truth about Mitsuru starts to unravel, leaving him in the dark about his own identity...