Prologue:
One day ten years ago two lazy skeletons tried to make a machine to go to another world.
It worked in a different way than expected. The machines activated at the exact same time. There was a flash that took over the underground.
Next thing any monsters knew they were waking up in an abandoned city on the surface... The same surface as each other... They now have no way home and they must work together.
Underfell and Underswap.
Not the most likely of pairing though they all managed to rebuild the city. They kept away from any humans not wishing to start a war.
Underswap monsters taking up most of the peaceful jobs and about half of the police officers. Though there is a handful or so of them who have turned to he crime life.
Underfell monsters took on a different role. They drifted more towards gangs and such. Though the other half of the police force is made of Fell monsters. As some of them are enough like the Underswap monsters to want to protect the peace. Though half of the crime fell monsters have even stolen from humans to help the city. Those type of crime fell monsters used their groups to do crime for good.
The two managed to find a balance and live in peace.
The city rebuilt and now fully functional for them to live peacefully and happily.
Just like back in their undergrounds.
Even if it's not really their undergrounds.
Though that was only the beginning.
AN:
I made this on my phone.
So hopefully I caught any autocorrects.
I hope you enjoy!
Kitkat.