ALL

It's basically another crappy Undertale AU thing. It's Sonictale (which is a thing) with just the characters swapped with their friends/siblings/etc.

INTRO (basically the same as Undertale's)-Long ago, two races ruled over Earth: HUMANS and MONSTERS.

One day,war broke out between the two races, letting peace exist no more.

After a long and bloody battle, the Humans prevailed.

They sealed the Monsters underground with a magical and powerful spell.

Many years later...

MT. ??? (The name is unknown yet.)

202X

Legends say who those who climb the mountain never be seen again.

[End of Intro, the name SONICSWAP in Monster Friend font appears)

It depends on the character, but all have some sort of magic. It's used differently for each character, though.

Just like Earth-gravity, physics, etc, etc.

First area of the game/whatever it will be/Ruins: SUPER ancient (because of cell phone)

Other parts-Just like today's technology. Good computers, cell phones, etc.