This time you will need to watch the animation with the sound in order to understand what is happening here. You can understand it without sound too but you might miss some details.
This is a well done critzisme of society i fell like it's more a critic about the world that could become or how it was in the 80's. Just get married, get a job, a kid, he move out, you die, the kid repeate the cycle.
The masks show how emotionless these people are, they don't live for themself just living in order to complete the purpose they got assigned at the start of there life. Once they got a kid they give him the same mission and once he move out they are sad not because the kid left but because they now there end is near.