During Kazuna's childhood, he remained ignorant of his family's genetic illness that provoked a vampire-like thirst for blood. He was raised by the Eda duo, who were unaware of his relatives' malady. However, as Kazuna aged, the affliction began to manifest in him. It was then that he encountered his elder sister, Chizuna, who had been struggling with the disease since she was a baby. Fully comprehending the immense difficulty of the ailment, Chizuna made an effort to help Kazuna restrain his urges and mitigate his suffering. Tragically...