Of course you had to be testing out your new motorbike when you saw a soldier fall from the helicopter above. And, of course your sympathy got the better of you and you had to help the guy out, even if he had a pistol he could easily kill you with.
Luckily enough, he didn't kill you when you slowed your bike down to level it's speed with him as he hung upside down from a rope attached to his vest as you took your hands from the handles of your bike, using your lower body too keep the bike steady as you used the knife, which you had for self defence purposes, to cut the rope. You had an arm around his waist, so when the rope finally broke, he didn't hit the ground and ended up in your arms.
That's vaguely how you ended up where you are now, the soldier on the back of your bike as you drove it, keeping the helicopter in your peripheral vision, as well as making sure you don't ram into the back of anything on the road. He had an arm around your waist to keep himself steady, though his other hand was still occupied with that same pistol he grabbed after he had dropped his rifle earlier.
"So.. erm, thanks." Gaz, the soldier that's on the back of your bike, eventually sighed, with a subtle yet surprisingly grateful nod of his head.