After your death you got into a borderworld between death and life,that the 7 deadly sins rule.They have the task to lead you to afterlife ,but since you died really young you want to go back to life.

Your only way to go back to the mortals is to get the seven deadly sins to open you a gate back.Thats your plan. When you enter the hall of the 7 deadly sins you witness only 5 of them and the in fact look like teenage boys-

(Kai-envy,Yeonjun-Lust,Taehyun-pride,Soobin -greed,Beomgyu-gluttony)