Ichigo and Zangetsu
"You ever had a girlfriend, old man?"
"-- okay, wrong question," said Ichigo. "Let's start again. You ever had an expression?"
"I do not understand why you are asking these questions."
"Call it boredom. Or," said Ichigo, "you might call it, oh I don't know the technical term but hey, let's call it enervation resulting from a shitload of fighting and way too much blood-loss for somebody who still has school the next morning. Oh fuck, calculus."
"You are tired."
"No shit. Hey," said Ichigo. "You any good at maths?"
He had a knack for trigonometry, as it turned out.