BOYNEXTDOOR’s 19.99 starts with a request and a friendly warning: “Everybody be quiet/Mom and Dad should not hear this song/You need to put on earphones/I'm sure you'll all agree, bro.” The hip-hop focus of “Dangerous” is a slight shift from much of the rookie K-pop group’s previous discography, defined by the bright, earnest pop sounds of boy banddom. 19.99’s single “Nice Guy” also asks BOYNEXTDOOR’s fans to follow them into slightly more mature K-pop territory, with some songwriting assistance from group producer ZICO. While previous BOYNEXTDOOR hits have crooned, “Baby boo, my sweetie, darling, think I love you more” or “Hey, hear me out, am I crazy or what?/I think my hand touched hers,” “Nice Guys” adds more bass-driven swagger to the mix: “Seoul is mine tonight/Let's rizz up all night/Let me tell you straight/Want to kiss you right now/I’ll get you all night.” But, unlike some operating in the pop group space, BOYNEXTDOOR is not looking to pretend to be older than they are, literally delving into the specificity of being around the age 20 in the song “20”: “What does a young guy know?/Some say I'm big enough, some say they're jealous of my age.” As with many other BOYNEXTDOOR releases, members were involved in the writing of all tracks, making the tongue-in-cheek specificity of the songs’ lyrics stand out in the K-pop rookie space. “Coffee splattered on clothes/Bus passing by/I guess the world is not on my side again today,” the rap in “Call Me” tells listeners. BOYNEXTDOOR may be experimenting a bit with 19.99, but the group's commitment to everyboy relatability is not going anywhere.