Riku tried very, very hard not to snicker. No really, he did! It was just that... Sora implying that their more mature evening together were a great way to relieve 'stress'... he really couldn't help himself.
"You know, there is also just so much studying a person can do. It might help clear your mind to write a better paper." Okay, so his foot was inching up Sora's leg a little. It was still totally innocent!