I really like the concept. Being the last one alive and being able to impart your words to unhuman like entities is a really bizarre and eerie thing. The song, sounds, and overall aesthetic also contributes to this feeling as well. Although I do think the stock image faces are a little goofy.
I think further work on this would involve adding more game mechanics and more individuality to each entity. You could add a system where entities could form relationships with each other based off various characteristics the player gives them. Also there is definitely an opportunity to leverage sentiment analysis on words/phrases given to the entities. Which you could then use to form a pseudo personality for them.