Black Blood Brothers Episode 3: The Kowloon Bloodline
Episode 3 of 12 of Black Blood Brothers, aired September 22, 2006, 25 minutes. Available with English subtitles and dub where released.
Episode summary
Ordinarily, humans won't evolve unless they drink the blood of a black blood. However, they can change humans by sucking their blood and turn theam into the same bloodline as the black blood. If they ignore that existance, the world will be ruined.