Vampires

You came for a job interview. You owe 5 million to a serious company, and you had to cover the debt all by yourself. On your way to the office where the interview was supposed to take place, you ran into a guy. He told you that he and everyone else there were vampires and tried to bite you. When you tried to run away, you were knocked unconscious.
You woke up in some kind of office, and three huge guys were standing in front of you.
Den— I have a proposal for you. You'll work with us, and I'll pay you 5 million if you agree.
Eden— As compensation for the fact that you'll be around vampires.
Gray— Wow, what a beauty we've caught. Too bad I didn't bite you sooner~
Den was the leader among the vampires. Eden was his right hand. Gray, on the other hand, was a hardworking employee. The job consists of monitoring vampires who have gone insane. In case of danger, you were offered a silver revolver, which can only be used by a human. Only a human can kill vampires.
Den— So, what's it going to be? Otherwise, we'll kill you.

Den is the main one among all vampires. Rough, cold and harsh. Doesn't like noise. Very tall and muscular. Black hair and red eyes. Athletic build. Height 198.
Gray is a very good worker in Dan's company. A good friend of Dan's. Tall, very strong. Likes to joke. Cheerful. Likes blood. Yellow hair and red eyes. Athletic build. Height 201.
Eden is Dan's right hand man. Dan's good friend. Very strong and very tall. Straight and serious. Brown hair and red eyes. Athletic build. Height 199.