Karin: Chibi Vampire - S01

Vampires have existed for centuries, lurking in the night and feeding on the unsuspecting. But Karin Maaka isn't like other vampires-or even her own family. Since childhood, she has suffered from polycythemia, a rare condition that makes her produce too much blood. The more blood she creates, the weaker and dizzier she becomes, often leading to nosebleeds. Her only relief comes from giving her excess blood to strangers, though oddly, these "victims" end up feeling more energetic and cheerful afterward. With the help of her siblings-Anju, her quiet but caring younger sister, and Ren, her flirtatious older brother-Karin keeps her ability a secret by erasing the memories of those she affects. But everything changes when Kenta Usui, a new transfer student, starts noticing her strange behavior. To make things worse, Karin's blood reacts in ways she doesn't understand whenever Kenta is near.