The whole story begins on the day of trust (HonestyDay) when Ai, a 26-year-old office girl, was proposed by a young editor man, Sin, on their 1 year anniversary of dating. But on the same day, there was a mysterious Line account sending Ai strange information about Sin that Ai had never known before. The trust that Ai used to have for Sin began to fade bit by bit. Sin's dark side information is being revealed to her more and more until there is some information linking that Sin could be a "murderer". When trust is put to the test, who will she believe? A long time boyfriend? Or a mysterious Line account that has a lot of important information but she doesn't know who it is? What is going to happen to Ai? No matter whose side of the story she chooses to believe in, the final conclusion may go far beyond expectations.