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.
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. Kaze Tachinu - Hikoukigumo
The lyrics about a "child who looked at the sky before death" resonate deeply with the character of Naoko, Jiro’s wife, who battles tuberculosis while supporting his dreams. She likened her friend’s short life to a