In this game, Sans unexpectedly meets Gaster. The latter tells the skeleton a lot of interesting things.

Sans gains tremendous experience and the necessary knowledge to fight. He decides to start the last battle against the person, that is, you.

He will make many attempts to stop the player in subtle ways. Gaster helps the skeleton, preventing him from dying. Will you be able to resist the conspiracy and see for yourself how the battle of the smart sides will end?