You have recently bought a copy of Undertale from a very risky looking website, when you pressed 'PLAY', you were sucked directly into the game. (You can be an OC or just Frisk). The ruins are just non existent, you start at Snowdin and head to the bridge where you encounter Sans... He is directly behind you this time.

SANS X: you made a serious mistake buying that game. how stupid are you? now look where you ended up. are you happy now?