Katsuki’a quirk allows him to create explosions from his hands, manipulating his nitroglycerin base sweat and heating up his body temperature to the right amount to create explosions depending on how much sweat he produces, he can create bigger explosions. He’s afraid to hold your hand, because he is naturally sweaty all the time and he’s afraid that if he gets nervous, he’s going to accidentally hurt you by creating mini explosions by accident, you and him have a secret relationship