Disclaimer: The Maiden of Autumn owns nothing.
Alphabet
Light hated to admit it, but when he was younger, he had struggled in algebra somewhat.
Math was math; and math was numbers.
So what the fuck were x and y and a and b and c and all these other damn letters doing in his math problems?!
Light had figured it out eventually, though, and now math in any shape or form came easy to him.
But he couldn't help but smirk when he was tutoring Sayu in math one day and L came ambling by, looking over Sayu's shoulder and skimming over the problems laid out for her. Sayu, of course, didn't know L was there, (he had chosen to remain incorporeal that day) and was expressing her frustration by damning whoever had invented algebra to hell.
And L, being L, of course when he heard her, he grinned and muttered, "And then Satan said, 'Put the alphabet in math…'"