Prologue

Frisk just wants Sans back. After Chara forced her and Sans to fall through the hole in Mt. Ebott, something happened to him. He's not here anymore, but this stranger claims to be both Sans and Dr. Gaster. Together, they continue through the underground, hoping to keep Chara at bay and find a way to bring back Sans. But what if they can't bring Sans back?
And what if Frisk falls for this stranger?

Adult!Frisk x Sans
Adult!Frisk x Gaster!Sans