A fight?

(This is an all au sans+classic sans)

"We were simply battling the enemies when suddenly a portal opened under us. If you were wondering no this time our ennemis aren't the bad guys. They were...."

Who were they're enemies?
Did they make a truce?
Why did sci sans came screaming at them?

All your answers to these questions are in this book, you just have to open it!

(19/5/2020)
By:Summer
Trash art by:me