Contains spoilers for this episode and earlier episodes.
Dal-mi's suspicions about the letters deepen as Do-san struggles with another old deception. A childhood memory reveals that his mathematics championship included an answer glimpsed on another contestant's paper. The praise that followed left him feeling undeserving, and his father's expectations still weigh on him. When his parents learn that Dal-mi is Samsan Tech's chief executive, the disagreement over his role forces Do-san to confront how much he has concealed from them.
A message from a Noongil user moves Dal-mi by describing what the app has made possible for a family. Do-san takes her and Won-deok to the seaside, hoping her grandmother can enjoy the view while she still has some sight. Their growing closeness does not settle the question of who wrote the letters. Back home, Do-san finally admits the truth about the competition to his parents, upsetting the image his father has treasured for years.
Ji-pyeong tells Won-deok that he has feelings for Dal-mi and wants to stop lying. Their disagreement hurts him, but he later agrees to collect a letter from the old birdhouse for Do-san. Dal-mi has accidentally taken her grandmother's phone and sees his message. She finds Ji-pyeong at the meeting place and asks why he is there. Calling Do-san, she asks where they used to leave their letters. He cannot answer, and the story she believed begins to collapse.