A Night Game is basically a porn game, this expression is more used when you are gonna play it on the night, because you don't have work or some shit and you don't have to sleep early and can stay up late.
Person 1: hey man, would you like to play anything tonight?
Person 2: Sorry man, I can't, I found this really cool Night Game I wanna try.
A guy who is usually tough and masculine during the day but who is cute and feminine at night. These guys, just like normal femboys, usually wear thigh highs.