Again and again

A certain Asshat named Dave Strider has been picking on young Karkat Vantas. He's bullied Karkat all of middle school and high school. It's senior year. But what's his motive? Why does he do it? Karkat has an online friend. He talks to him on a daily. But who is his online friend?
(This is a crappie fanfic because I'd die for this ship.)

Characters are not mine. They belong to hussie.
Anyway yeah let's get to the book.