Letter to Hong Kong is an unreleased video shown at both the Seoul and Busan venues of LOONA Cinema Theory: Up & Line. It features ViVi recording a video message in Cantonese to her parents, following her activities with LOONA 1/3.
Synopsis[]
At the start of the video, she is seen practicing and joking around with the other members of LOONA 1/3 in LOONA's practice room, before going on a trip with HaSeul to an aquarium. The camera then zooms in on JinSoul, who is seen in the background wearing the same eye-patch and uniform as in Sweet Crazy Love, before suddenly cutting off, followed by the Sweet Crazy Love music video.