Black Magic (Yu Yu Hakusho; Hiei Jaganshi).

We were bonded to each other like the sun was to the moon. In a way, I was the sun and he was the moon. My heart beat was proof enough that I was alive, yet his wasn't beating. He was a demon who challenged me in every way imaginable, and I hated it. Just like the sun didn't like to be hidden behind the clouds through a storm, it'd always find a way to maneuver and shine through the darkness. Then again, we weren't just dealing with clouds blocking the sun; we were dealing with black magic.