Mysta gets flustered when you pull his collar to kiss him. He has said before that maybe he needs to be taught a lesson, right? And he's usually the one leading the physical affection, so I think if you assert a bit of dominance on him, he's going to be taken aback, in a good way of course. He has made it a habit to stop right before he presses his lips onto yours and scan his eyes over your face for some reason, probably to take a bit of time to admire your features. It's simple, the next time he does that, just grab the collar of his shirt, and put your lips onto his. The first indicator of his fluster would be the strangled noise that escapes his throat and vibrates against your lips. Give him a deep kiss, and when you part, you'll be greeted by his widened eyes, and then his eyebrows would curve in a slight frown. "Fucking hell." he would mutter before smashing his lips onto yours in a rougher kiss.
