Il Mare

The story opens with Eun-joo moving out of the seaside house Il Mare. She slips a Christmas card into the mailbox, asking the next resident to forward her mail. The card is dated two years in the future, which confuses Sung-hyun as he is the first resident.

Sung-hyun, the first resident, receives the card and is puzzled by its two-year-distant date. He reads the message and begins corresponding with Eun-joo, even though she exists in a different time frame. The mystery of the mailbox starts to unfold.

Eun-joo and Sung-hyun realize they are living two years apart: she is in 1999, he is in 1997. They discover the mailbox at Il Mare can pass letters between their times, effectively linking their fates. This discovery becomes the core mechanism of their evolving relationship.

Using the mailbox, Eun-joo asks Sung-hyun to retrieve a tape player she lost two years earlier. He manages to pull the tape player through the portal, proving the exchange can extend beyond words. This tangible proof deepens their bond.

Sung-hyun asks Eun-joo to obtain a book about his father, hoping to understand him better. She is hospitalized for a minor traffic accident and cannot deliver the book before Sung-hyun's father dies. The failure creates emotional distance and motivates him to re-engage with his own life.

Eun-joo and Sung-hyun continue their correspondence and stage solo dates across their own timelines. Eun-joo takes him to an amusement park, following her playful instructions, while he brings her to a restaurant where she drinks wine he left two years earlier. The dates deepen their connection despite the temporal separation.

They decide to meet in person at a beach two years in Sung-hyun's future, a moment that would bind their fates beyond the mailbox. The plan gives them a tangible goal and a shared dream across time. This creates a bittersweet anticipation as the two timelines converge.

Eun-joo arrives at the agreed beach, but Sung-hyun does not appear in her timeline. He later visits the beach and is moved by its beauty, realizing he must create something meaningful there for her.

Inspired by the coastline, Sung-hyun resolves to design a house there for Eun-joo. The project becomes a symbol of their intangible bond and his commitment to a future they cannot fully share.

Eun-joo encounters her ex-fiance at work and contemplates their broken engagement. She asks Sung-hyun to intervene and prevent him from leaving two years in the past, forcing a clash between love and fate.

Torn between desire and commitment, Sung-hyun writes to Eun-joo offering luck for her and her fiancé's future and decides to aid her by stepping back. He makes a personal sacrifice for their chance at happiness.

After receiving Sung-hyun's heartfelt reply, Eun-joo visits his school and discovers that he died in a traffic accident two years earlier. She realizes the day she last met her fiancé, she witnessed a pedestrian being hit, and that pedestrian was Sung-hyun.

She discovers the house being built on the beach was designed by Sung-hyun for her, linking his art and their love across time. The revelation confirms the depth of his commitment despite his untimely death.

Eun-joo rushes to the mailbox and sends a plea for him not to go. The final moments reveal that Sung-hyun did receive her warning, he never intervened to prevent the accident, and eventually they meet in the present. The movie loops back to the start as they finally come together.