The story begins at the end of 1999, as voiceover actress Eun Joo moves out of a seaside home named "Il Mare". Before leaving, Eun Joo leaves a Christmas card in the mailbox, with a message asking the eventual new owner to forward any mail of hers to her new address in the city. Meanwhile, exactly two years prior in 1997, Il Mare's first owner, architect Sung Hyun, receives Eun Joo's card. Thinking it to be a joke, he writes back to Eun Joo and asks her not to tamper with his mailbox anymore, while pointing out that the "current year" is 1997. However, after a bit of back and forth banter, all doubt about the magical properties of the mailbox are soon erased, and Eun Joo and Sung Hyun begin sending regular correspondence to each other. In addition to finding out that they are both kindred spirits, they come up with new uses for their unique connection: Sung Hyun is able to return a tape recorder that Eun Joo lost two years ago, while Eun Joo is able to send back a still-unpublished book by Sung Hyun's estranged father. Eventually, they agree to meet in person, an uneasy task given their separate time periods. Though the agreed upon day is only a week away from Eun Joo's perspective, it is still a full two years from where Sung Hyun stands. Will these two lovelorn pen pals meet?