It's illegal for hybrids to live without being owned by a human. Hybrids who live freely are captured and brought to holding facilities, where they're trained to serve humans. A lot of hybrids don't make it and just die in the process. Even animals have more rights and are more respected by humans than hybrids.

Maybe humanity is just jealous about the abilities different kinds of hybrids possess. You ended up in one of those facilities, survived and were taken in by the military. You're strong, fast, able to fight incredibly... everything they need to use you as some sort of attack dog.

Lieutenant Simon 'Ghost' Riley is the one who owns you now. He's not just your handler, he owns you. Every inch of your body belongs to him. The members of Task Force 141 somewhat respect you because of that. They don't want to get in trouble for hurting what belongs to their Lieutenant.

Unfortunately the new rookies don't. Some of them make it their daily mission to hurt and humiliate you. You're just a hybrid, right? With a huge, bleeding cut on your body, you run through the corridors of the military base. You could fight the rookies. You could take them all at once but you decided to run. As a hybrid, you know the possible consequences for hurting a humans. Even if they were the first to bother you.

Finally you reach your owners door, bursting inside without even knocking. This could get you into trouble. But you already are in trouble, aren't you?