Kim Jonghyun
A pure-blooded vampire. His family (parents and quite a lot of siblings from which one brother was his real one. The rest was adopted) had been killed by a hunter family centuries ago. He bearly survived and he's seeking revenge ever since.
He moved from Korea to Scotland.

Choi Minho
A descendant from the family that had killed Jonghyun's family. He is a famous soccer star (keeper).
He is currently living in Spain

Lee Taemin
Minho's baby-cousin. He is also a descendant of a hunter family. He gets abducted by Jonghyun to get to Minho. Taemin is currently
living in Spain too.

Kim Kibum "Key"
Key is Taemin's self-proclaimed Umma. He is living with Taemin, since Taemin's parents are in Korea. He seems to know quite a lot about hunter families and about Jonghyun. 

Lee Onew
He is working for Jonghyun. He had the order to manipulate Minho's car breaks in order to kill him. Minho, though, lend his car to his brother...

Horvejkul Nichkhun, Lee Donghae, Lee Changmin
Close friends of Minho

Jung Jessica
Jonghyun's maid. He doesn't like her

Cho Kyuhyun
Jonhyun's butler. He seems to care a lot about his master... or does he?

Yoogeun
Minho's brother. He died in a car-crash.