Karin the blood making vampire.
The original manga had some unconventional ideas to make it not just another vampire story (including but not limited to the blood making bits), but the anime reduced it to mostly about Karin's large boobs, which makes it quite disappointing. Added to that was the anime original characters, all of them are borderline annoying. The only saving grace was that Maki was better represented in the anime in the manga, in all other respects I would recommend reading the original instead and not watch the anime.
+ Kadokawa / Google