Seo Kang-hoo is a tall, silver haired vampire born in an elite family. He is first introduced into the story when Yoo da-in comes by his school to meet her friend, Sun-Woo. Seeing there is a forest on school grounds, Yoo Da walks about. But upon seeing Seo Kang-hoo attack a female student, she strikes him in the back and then in the face with a roundhouse kick. He later reappears when he attempts to stop his brother, Seo Ji-hoo, from killing humans in a secluded barn.
Seo Kang-hoo's personality is completely different from Seo Ji-hoo. He is seen as a cool and collect student that is able to think rationally in difficult situations. To those at the school and among the vampire community, he is frequently viewed as cold and unfriendly despite his popularity. Seo Kang-hoo is actually kind and always thinking about others. But as the story progresses, his strong feelings for Yoo Da leads him to make impulsive decisions and even throw away his pride if it was for her sake. Throughout the books, however, he consistently continued to make decisive decisions.