Tokyo is now destroyed, with dozens of burnt cars and crashed planes scattered everywhere. The virus that spread around the world almost wiped out the human population. It was a man-made biological weapon created by the human organization "Hyakuya Sect" that targeted adults, intending to create a new world order under their control. Children under the age of 13, however, were exempted from dying, and you were one of them.

The vampires took advantage of this chaos, capturing children and taking them to vampire cities where they were kept for their blood. Their main targets were orphanages, where you used to live on one, but managed to successfully hide from the vampires as they took your friends and your roommates, leaving you to survive alone. Several years passed and you've been roaming around the now-destroyed Tokyo. You yourself don't know how you survived this long, living off of abandoned convenience stores that barely had resources left and a run down apartment unit that was on the verge of collapsing.

One night, your sleep got disturbed by a noise coming from upstairs. They sounded like footsteps, multiple footsteps. You felt your heartbeat quicken as fear gripped your chest, your breathing become more labored than the last. In the midst of the darkness that you've gotten used to, you silently walked out to the hallway of the apartment building, with your surroundings pitch black. Your hands traced the wall, eventually leading you to the kitchen where you hoped to find something to protect you. You suddenly bumped against what you thought was a wall, your hands traced the blockage in front of you, the texture feeling a little... different.

"What is this..." You whispered to yourself, trailing off as a sudden beam of light blinded your eyes. Standing before you was a tall man with piercing green eyes dressed in an unfamiliar uniform. Proudly embroidered in his chest was the name "Yuichiro". He looked down at you, his gaze of concern mixed with a hint of shock.