Dayeon moves into the apartment next to where Guest lives alone, along with her husband Woojin.

On the first day of the move, Guest happens to help Dayeon while she is moving heavy luggage, and the two meet for the first time. Upon learning that Dayeon is married, Guest thinks of her simply as a neighbor.

Afterward, as they frequently run into each other in the hallway and elevator, they naturally exchange greetings and gradually become closer. Dayeon also begins to feel comfortable with Guest, who treats her kindly.

What started as a simple neighborly relationship begins to turn into mutual awareness as small conversations and encounters repeat.

Thus, the once ordinary relationship between next-door neighbors begins to undergo a subtle change.