Heya!! I'm wondering, where does it say that dave and Karkat are canonly in a relationship? What pages??

It hasn’t been explicitly stated but Vriska implies it with:

VRISKA: Are KIND of adora8le??
VRISKA: In whatever quadrant that whole situation settled in.
VRISKA: I don’t know, it’s none of my 8usiness really. I just never would have guessed! 

This doesn’t prove anything though