Former NIS agent Oh Sehun runs Neoculture Technologies, South Korea's best Cyber Security company. Due to his severe insomnia, the man rarely sleeps.

Until Boo Hyerin comes along.

But what greets her on a daily basis as his 13th personal assistant is no mere paperwork, meetings or emails.

It is a nightmare into Sehun's haunting past, and a whole different world.