>>189292777The opening theme song.
Honestly, I didn't understand the series on even the most shallow level when I watched it years ago. "Recently" I heard someone mention a subplot from the show about the angels' attacks becoming more creative over time to the point where they attacked under the guise of a normal human boy, and then later a mist.
And I said, "Wait, what? Did that happen? Oh..."
I don't know why I watched the whole thing if even that went over my head.