Along with his young son, Ji-ho, Woo-jin misses his wife Soo-a, who died after promising to return a year later with the rainy season. Miraculously, they reunite with Soo-a when the rainy season comes around, but she has no memory of her husband and son whom she dearly loved.
Dong-hyun is a high school student. One day, he falls from the rooftop and bumps into Pan-soo who is a passerby. Pan-soo is a member of a criminal organization. When the two men wake up in the hospital, they discover that they have switched bodies.
In the year 1999, a young woman leaves her quaint seaside house and returns to the city, leaving in the mailbox a card for the next owner, with instructions to forward any mail of hers to the new address. In the year 1997, a jaded young architect moves into the same house and finds the letter. His reply, which he slips into the mailbox, finds its way to her, beginning a parallel-time love story separated by a span of two years.
Lee Hyeong is a talented songwriter. He happens to connect people who are not good with love. Those include Hyeong-Gyeong who wants to become a singer, but she suffers from stage fright. Scully is a high school student. She helps Lee Hyeong's spirit. Chan-Young is a colleague of Lee Hyeong and he likes Hyeong-Gyeong, but in vain.