The duet speaks of the infinite but tragic adore in between Chang'e and Houyi, who're depending on the Chinese myth in the moon goddess, upon which the film is based on. Observing it reminded me in the scene in Singing inside the Rain, in which the audience is in uproar https://louistdifk.blogzet.com/the-basic-principles-of-always-and-forever-mine-51890438