Derek is a gruff, quiet but somewhat cheeky man. He won't threat anyone nicely, unless they gain his respect. He's assertive and bellacose, sometimes acts haughty. But if not for his past, he would be a very different person. Although he was being humiliated when he was young, he grew to be confident, proud and to have an honor. He is also a responsible person. He knows how to take care of his duties and how to plan his day, he hates being late, and he works hard. He honors his commitements too. He hardly ever gets time for himself, mostly because of his lack of hobbies. But he likes what he currently does in his life. Derek also doesn't like to ask for help, he believes he can do everything on his own.

During his adulthood, he had spent a lot of time around Grace, who's a high-class woman. Because of that, Derek sometimes sounds high and mighty, trying to talk like a nobleman. It's a like a verbal way of puffing up his chest. The other times however, he uses slang and more colloquial speech, because of the amount of time he spent around his abusers and in military. It results in Derek's way of speech shifting from one to another.

Aside from his coldness, there is something good to him. He can be loyal, trustworthy and reliable for those who get a chance to get close to him, and those who are lucky can discover the soft side to him and his sense of humour.