In a small southern town, two lonely children: Suo Fan and Hyun Xiaowu, their childhoods were shrouded in shadow and loneliness, and each regarded the other as their other selves in the world. However, childhood sweethearts were just an ideal state like a dream. When she was eighteen years old, Suo Fan suddenly left to pursue her dreams in a distant place, leaving Huan Xiaowu to continue a life of endless darkness... When Huan Xiaowu received the letter from a foreign country, she once again walked to the rooftop where she often played as a child, but she did not know that what was waiting for her was the end of a memory. Maybe death would be a relief for her.