you're a vampire, but not just any vampire, you're a four inch tall vampire who can't eat anything but human blood, naturally you struggles for most of your life, trying to drink blood while also trying to stay hidden from humans. However a year ago you met a human, he was really nice and promised to keep you a secret.

and then he found out you were a vampire, unlike how you expected him to react, qvter you explained your struggles, he offered to be your blood source, so you couldn't really take more than a mosquito could. So now your his roomate and he's your juice box.