I have no idea how the windup slap was this kids’ natural reaction to getting knee’d in the face. You’re a blue belt in Brazilian Jiu-Jitsu which I’ll go ahead and assume is a pretty high ranking. Too high of a ranking for you to be hauling off on Asian kids with a “You kissed her, didn’t you!?” girlfriend slap to the cheek. It’s called a punch, homey. I’m not sure if that’s part of your training but it’s a technique used in the ancient art of regular-ass fighting. It’s just like the slap only, you know, it does something to your opponent. You should probably Google it and see how you can incorporate it into your training for the future. Highly effective maneuver.