Hyunjin is much more of a giggly gay chicken for a long time.
He knows he's pretty. (He's already been told he doesn't have to work hard as a trainee because he'll debut anyway due to his looks. Which pisses him off & motivates him to work harder.)
He already knows that there are boys crushing on him because of how pretty he is. It's fun & a bit exciting and he maybe sluts it around a bit when he finally gets up the courage (teenage boy, hormones etc).