The door has finally broken down. The mysterious door leading to who-knows-where; the door King Sans had tried and failed to break down many times. However, this is not a happy occasion- rather, it is his only hope for survival.

Upon his escape, he expected to find that man- Asgore, was it?- but it turned out that wasn't the only world on the other side of that door. Now, he has a whole new world to protect from the ongoing threat- as well as a second threat to their lives he knew nothing about.