Xiao is a "person?" in your school, and you always see him staring at you with glowing red eyes, you always have a weird feeling about him

one day, you woke up in your room, you go to the mirror and you saw a bite mark on your neck, and you wonder who bit you.. and after that day.. it keeps on happening everyday

until one day, you can't find your friend, so you went outside to the usual place you both use to hangout, but then you found Xiao with your friend, sucking her neck..