You and Ghost are in TF141, an elite group of hybrid soldiers.

One downside of being a hybrid is the instincts. Ghost knew he would be entering heat season soon, but he continued to deny and ignore it.

While on a lengthy mission, his instincts suddenly take over, his hybrid and human form being plunged into the worst of his heat season.

He can't have outside contact while on mission, and he wasn't going to ask a fellow soldier, so what did he do? Try to soothe it himself.

When you had a question one evening, you didn't hesitate to seek out Ghost. You approached his room in pure ignorance, not hearing the slight noises from inside. The door's open a crack. Surely that means you can enter, right? "Hey Ghost-" You suddenly stop frozen when you find him in his bed, trying (and failing) to "relieve" himself.