15-Year-old Lin Xia and 17-year-old Cheng Yuan met in an environmental protection invention competition. Cheng Yuan joined the army after taking the college entrance examination and agreed to finalize the relationship on her 18th birthday. After a brief reunion, the two began a long-distance relationship. The girl shared her college moments, and the boy replied to her letters in the snow. Until he died in the line of duty, the data signal stopped abruptly. In the eternal farewell between heaven and man, their love turned into the buzzing of gears and the flow of the Milky Way, completing a promise that spanned life and death.
