Well, if it's not because Ku Hye Seon, I would not watch this drama hahaha. First impression, this drama is too mainstream. It's about vampire and as the title says, blood. But, the positive points you can get is a biology, chemistry, and medical knowledge (as expected from kdrama). Things made me want to watch it until end are the super-modern technology Park Ji Sang and Hyun Woo have. Hyun Woo is a genius man, and I enjoyed anything about his experiment even it's a fiction. If you say why this drama is just 7s on its rating, for me it's the ending's fault. Its ending ruins all of the story. It's like this drama will release its 2nd part or sequel. You will hold so many question after see the last part of the last episode. And yeah, I think this drama is not over yet. Let's see if there is a sequel. Anyway, I love Park Ji Sang's character, cool and cold. HAHAHA.