Red

Red. Bright red. That was its color. Bright, but dark. It was beautiful. It was on my hands, my clothing, the floor; it was on his too. We laugh, because it was our first one. We laugh because it felt great. We laugh, because we just killed someone.

Or-
AU where Kageyama and Hinata are a couple (literally) that goes around killing people for sport. Basically, kind of like a modern day Bonnie and Clyde minus the robbing,gang members and add in more killing.
[I promise it's good]