This BGM has a gentle, pretty, fantasy feel, but also seems a bit simple and unaffected. The recorder, the zither, and the accordion, which appears only for a moment, create such an atmosphere.
The balloons that have flown out of reach gradually fly higher and higher in the sky. You were a little sad to see such a scene, but thought it was beautiful on my way home. That's the atmosphere of this song. Maybe.
In other words, it is a bit sentimental.