A month ago, Doyoung lost his older sister, Hwayoung. The air in their house seemed to freeze in the face of the sudden accident. While cleaning up after Hwayoung's room, Doyoung discovers her sister's diary entries. Curious, Doyoung begins reading the diary. However, Hwayoung keeps appearing in Doyoung's dreams, making it impossible for him to sleep... Doyoung is convinced that the dead Hwayoung keeps appearing in his dreams because she has words she never got to say before. Doyoung seems to hope that her older sister will convey those feelings on his behalf. Doyoung sets out to find "that person" to whom her sister desperately wants to convey her feelings as she journeys on her final journey...!