The rift in Taeyeon and Jessica's friendship continues to go untreated after a terrible fight over a person they both loved. Despite Taeyeon's feelings, Jessica wins him over but at the price of losing her best friend. In the end, Jessica haplessly clings unto memories of their relationship with hope, while Taeyeon chooses to ignore their situation believing to move forward. But when Jessica and her boyfriend break it off, Taeyeon's suppressed frustrations over her manifest once more in the form of a fake anti-fan's letter. Surprisingly, Jessica decides to reply. Taeyeon chooses to play along and the two begin to exchange letters in secret, with Jessica never knowing the real identity of her pen friend. Taeyeon, however, finds herself falling in love as Jessica's heart emerges from the pages of her letters and she has to now keep her feelings hidden, afraid of disturbing their already precarious relationship. How will she fair? What does Jessica actually think of Taeyeon? Is it already too late for them? Nothing could be more worrying than sealing a letter with a secret.