Fangs

Attacked by vampires at a club, nineteen-year-old En survives after being bitten and turns into a vampire himself. He is then found by Ichii, a vampire from the organization "FANGS" who becomes his guardian. To satisfy the vampires' urge to suck blood, the organization encourages a "pairing system" where two vampires agree to support one another. At his first pairing party, En attracts a lot of vampires due to his status as a "virgin," and thus declares in a panic that he will become Ichii's pair...?!

(Source: Gentosha Comics, translated)