A love letter, which has constantly been sent for fifty years, lasted their love for half a century. Since she was ten years old, Naeun had been receiving mysterious love letters, until when she was 22 years old, she experienced a rare sun storm while driving with her friend, Eunji. The accident brought the two friends back to fifty years ago, where they met Sunggyu and Myungsoo, the angels who used half of their lives to protect them. Two pairs of young men and women met and fell in love w