Vampires are supernatural creatures that feed on human life essence at night. while most vampires have been around for centuries, high schooler karin maaka is unique among her kind. she suffers from polycythemia, a rare disorder that causes her to produce excessive amounts of blood periodically. the more blood she produces, the more anemic and lightheaded she gets, resulting in frequent nosebleeds. to solve this problem, karin forces excess blood onto random strangers, which makes them feel livelier and happier than before. her siblings, anju and ren, help her keep her abilities a secret by altering the memories of affected humans. however, things become complicated when kenta usui, her newly transferred classmate, finds her behavior suspicious. additionally, karin's blood reacts unusually to kentas presence.
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