Comment by Anim _// on Cry Me a River - Chapter 19

@Anim _// so what's happening (as much as i know) is that Jitae's older brother that is Jian hired almost every employee in Jitae's house to keep an eye on him (as instructed by Jian's mother) including Mi Eum. Jitae knows that every worker is a spy of his older brother and mother. 
Mi Eum is hired/blackmailed by Jian to keep eye on Jitae by keeping Mi Eum's father as hostage. 
Now that long haired guy is Go Hajoon whose batch name is with Mi Eum. 
Apparently in past Mi Eum's father kidnapped Jitae which almost resulted in Jitae's death and maybe that long haired guy aka Go Hajoon knows about this all kidnapping case too.
But Mi Eum doesn't know that his dad is the former kidnapper of Jitae cuz he had a short term memory loss around the time when Jitae had been kidnapped. 
Jitae told Mi Eum that he knows he(Mi Eum) is a spy but he won't tell anyone cuz it doesn't make any difference. So they that is Jitae and Mi Eum made a deal where Jitae will use Mi Eum's body in return Jitae will help Mi Eum to find his dad who is being held hostage by Jitae's older brother that is Jian 
(FOR NOW THIS MUCH HAD HAPPENED, HOPE THIS HELPS ALTHOUGH I'M KINDA LATE BUT YEAH!!)