The film opens with a man being interviewed about his sister, who has recorded a video diary in which she makes a shocking confession to her friends and family. Purporting to be a true story, the bulk of the film is presented as a reconstruction of actual events.
Hyun-joo announces to her younger brother Jae-min and his girlfriend Ji-eun that she has an important confession to make, and asks them to record it on video. After issuing an apology to her parents, she reveals that she has been hiding a painful secret and is not like normal people; she is in fact a vampire. Jae-min and Ji-eun initially think she is playing a prank, but to prove her sincerity Hyun-joo bites into her wrist and starts to suck her own blood. She goes on to disclose further details of her life as a vampire, and dispels many of the common myths associated with the legend. Having heard of others like her overseas, she has decided to join a community of vampires living in England.
Going out at night to attract less attention, Jae-min films his sister as she feeds on a young woman in a telephone box. He and Ji-eun later talk to the woman, who remains unharmed, and she tells them that the experience was not painful, likening the sensation to an electric shock. The events prove to them that Hyun-joo is telling the truth.
Some time later, Ji-eun visits Hyun-joo who is now living in England. Curious to know how it feels being bitten by a vampire, she asks Hyun-joo to suck her blood. Choosing the inside of her thigh, Hyun-joo begins to feed on her friend.