Devil. A word that usually signifies demons, Satan, and all the evil in the world. But here, it is simply a popular, high-paying career with a stable income.

Woo-hyuk is a part-time convenience store worker struggling to pass the official Incubus recruitment exam, which opens only once a year. One day, he receives a bewildering proposal from Si-woon, the grateful friend who has consistently helped him for a long time...

Do you really want to pass that Incubus exam that badly? Then practice with me.

And so, their Sex Class begins to prepare for the exam... It feels amazing, but... is it really okay to do this between friends?!