Bong Joon-Ho keeps us guessing in his best picture winning masterpiece.

Intro song is from largely forgotten game Parasite Eve:
https://www.youtube.com/watch?v=PM2cBVf9XJs

Interstitial music is from the Parasite film's closing credits. This song does away with any happy reading for the ending of the film.
https://www.youtube.com/watch?v=e2TPDhUoRLw