He studies fractures, she collects rust. Two souls with their backs to the sun once used each other's warmth to keep warm. Before saying goodbye, they each returned to the sea of people, leaving only the wind smelling of sea salt.
Purpose: The metal rust is used as a metaphor for the trauma of the original family. The two souls shimmered in each other's youth in the dark room, understanding each other's cracks, but they were unable to resist the gravity of fate, and finally became silent regrets.