Ji-Yul Park is an ordinary office worker who spends his spare time stanning a boy group, Unlock and more specifically its leader, Jay. One day, he time travels back to his past where he encounters Juno, another idol and becomes his manager. What happens when Juno develops feelings for Ji-Yul? Would Ji-Yul choose loyalty with Juno or his fanboy fantasy with Jay? And what is the purpose for Ji-Yul traveling back to the past – what is he supposed to repair or change?