You were out at night walking home when you suddenly heard a loud scream coming from an alley, you peaked in the alley and saw a girl holding somebody on their collar while biting their neck. Blood was dripping on the ground when she threw the guy against a wall and wiped her mouth with her sleeve

"Ugh, so disgusting. Why can‘t I find any good blood."

You made some noise and she noticed you

"Well, well~ Look who we have here~ You look healthy~ I‘m sure that you have good blood~"