He just enjoys the idea of spooking the other. Maybe Gokudera will set his pants on fire. Yamamoto will never know. It'd be way too funny watching him try to put his butt out. Gokudera's got to hold back his attempts. It's too soon... There isn't enough sense of security.

He has not won! Gokudera won't let him. Having his hair touched makes him raise his shoulders and draw his head back while he swings an arm. It's to either punch, push, or slap but it's all to communicate, "Don't touch me!"

Rude!

"It would!" That's it, he's clicking that lighter behind Yamamoto. There is actual flame approaching him. It'll either be the back, the butt, or whatever else he can reach, but Gokudera is Going For It.