Board Thread:Questions and Answers/@comment-32115911-20170526153725/@comment-29460876-20170528155540

It looks like, in old mythology, people believed that aliens lived underground but, now we believe they live in space somewhere because, it is yet to be explored. Undertale doesn't really say much about the world on the surface because, it is not important to the story. The Undertale world is probably like our world except, the monsters live underground.