Every summer, she writes a letter she never sends. This year, someone sends one back. Hye-jin has always believed in love-the kind that makes your heart flutter and your pen move without hesitation. But after a painful goodbye years ago, she's kept her feelings locked away in a box of unsent letters written each summer, addressed to the one who got away. Now living a quiet life in Seoul, working at a small publishing house and sipping coffee at her favorite café, Hye-jin never imagined those forgotten letters would come back to her-literally. When one mysteriously appears in her mailbox, written in response to something she never mailed, her heart stirs with questions she can't ignore. Who read her words? Why now, after all these years? And could the one she's been writing to... have been closer than she ever imagined? As she follows the trail of the anonymous admirer across the city-guided by cryptic clues, shared memories, and heart-racing encounters-Hye-jin must face her past, trust her instincts, and open her heart one more time. Because the greatest love stories don't always start with a confession-sometimes, they begin with an unsent letter. Perfect for fans of emotional K-dramas, heartfelt second-chance romances, and slow-burn stories filled with mystery, charm, and poetic longing.