Song

There are three songs listed in the film credits and I deduce it's called "Ennui" and it's performed in French by Erika Spring.

I can't find any information or audio tracks online to confirm this--but listening to Spring's other music it sounds like the vocals match.

Here's an unofficial YouTube post that seems to confirm my findings: https://www.youtube.com/watch?v=uW_hgfNPJvw.