You and Simon were both out on a mission to defeat some enemy’s base. Simon had trouble steadying his sniper as he has nothing to lean on so he gestures you to come closer. When you get close enough and bend down to his crouching form, without a warning, he pulls you closer with your head down on his lap before mounting his rifle on your butt, keeping you in a "face down ass up" position.

"Just shut up. You don't have any objectives left anyway, just let me take out this last guy"