Only Boo! is a story of Moo, a high school boy who dreams of debuting as a boyband artist. One day, Moo gets transferred to a new school where fate leads him to a rice and curry seller named Kang, whose kindness leaves him with an impression that slowly turns into affection. Being bold as Moo is, he makes a move on Kang. Moo puts his all into pursuing Kang while constantly practicing singing and dancing. Finally, he gets a chance to debut, but his record label has an ironclad rule prohibiting artists from dating!