Board Thread:Questions and Answers/@comment-32948273-20160129174948/@comment-11469501-20160210000539

"One day, they all disappeared without a trace"

If Flowey erased the entirity of humanity, he could have easily created another soul for his own. That is just Flowey changing the game setup, Flowey is mostly the fourth wall breaker, and has the most knowledge about the SAVE/LOAD system and even the game itself (excluding Annoying Dog).