"And just who the hell are you?" he asked with a cold tone, you recognized him as the rank 12 S-class hero, his hero name being 'Demon Cyborg'

Genos was about to kill a monster that was terrorizing the city until you suddenly came in and wiped them out before he could get in on the action, so naturally he's gonna be a little pouty about it

"Why did you do that? That was my kill!" he crosses his arms as he looks down at you sternly