Kaneki Ken is a ghoul. In the beginning, he tried to hold onto his human side desperately, despising the idea of craving human flesh. But after failing again and again at being normal, he has accepted his fate. Deciding that he as a dangerous predator, should be isolated. 
Kaneki has a kind heart, but he is cold to others, and does not allow his true colors to shine. His greatest fear is losing to his hunger and killing a human. He is barbaric in battle, and is a person to be feared. 