The song was not originally written for the film. It was the debut single of (then Yumi Arai), released in 1973 when she was just a high school student.
Decades later, Miyazaki heard the song and felt its "ethereal" quality was the perfect match for Jiro’s story of creating beautiful machines that were ultimately destined for destruction. Thematic Resonance in The Wind Rises Kaze Tachinu - Hikoukigumo
In the context of the film, "Hikoukigumo" serves as a bridge between Jiro’s professional ambition and his personal grief. The song was not originally written for the film
Just like a vapor trail, Jiro’s "ten years in the sun" (his creative prime) and his time with Naoko are intensely beautiful but painfully short-lived. Thematic Resonance in The Wind Rises In the
She likened her friend’s short life to a "vapor trail"—a white line in the sky that is brilliant for a moment before disappearing.
The song plays into the film’s central question: how does an artist create something beautiful in a world that is broken? Jiro’s planes are masterpieces of engineering, but they are also tools of war.