Karin is a vampire, but as fate would have it she is a freak among her own kind; for Karin doesn’t drink the blood of her counterparts – she is cursed to be a blood maker, forcing her to inject her extra blood into her victims. What’s worse is that if she doesn’t find an outlet for the blood in time, it explodes in a massive nose bleed of impressive volume. In Karin's twisted day-going state, she finds it nearly impossible to find safe victims; so, nose bleeds are a major problem. When transfer student and new classmate Usui Kenta proves to have exactly the kind of emotions her vampire nature most enjoys, she finds herself in comedic dire straights!
Sumire Takahana was a once normal high school student, until one day, she picked up a mysterious brooch and began to see soul-eating demons known as Virus. Now under attack, Sumire was saved by the owner of the brooch, Lucia, and Lucia’s Vaccine-loaded gun. However, instead of shooting the Virus, Lucia accidentally shot Sumire herself, turning her into a living antivirus. Together, Sumire and Lucia will try to uncover the secrets of the Virus before they devour all of humankind.
The atmosphere of both shows are rather similar. While watching VVV, I was reminded time and again of Karin, through the music, character design, and styling. Story-wise, they're pretty different, but both are aimed at the same audience, so if one was enjoyed, the other might be as well (although subjectively, Karin was much, MUCH better).