Jiraiya promptly sprayed sake all over the table. 

"E-ehhh? What? How they work? What do you want to know?" he asked, wiping his mouth on the back of his sleeve.

Naruto scowled fiercely. "You know, you know, what they like and stuff."

"Oh, that's what you meant..." Jiraiya heaved a deep sigh of relief and poured himself another bowl of sake.

=====

"And one last thing," Jiraiya opined, gesturing grandly at the fascinated Naruto with his bowl. "And this is very important, so I want you to listen with all your might!"

"Yes!" Naruto squinted at him in fierce concentration, fists clenched in front of him. "I'm listening!"

Jiraiya leaned forward, closing the distance between them. "What you must remember about selecting women is this: the bigger the breasts, the smaller the heart." Satisfied, he sat back and took a long drink, but the satisfaction faded when he saw the look of utter incomprehension on Naruto's face. "... eh?"

Naruto tilted his head to one side. "Their hearts come in different sizes too? But, but, perverted old man, doesn't that make them harder to kill?"

"No, no, no!" Jiraiya heaved a deep and windy sigh. "Look. You remember Tsunade, right? Breasts out to here?" His hands cupped descriptively about a foot away from his chest. Naruto nodded, uncomprehending. "Now, what kind of a woman was she?"

"Oh!" Naruto crossed his arms over his chest and nodded furiously. "Her heart must be the size of a walnut! No wonder getting stabbed through the chest didn't kill her!"

Jiraiya's fist lanced across the table and thumped Naruto soundly. "Metaphorically, useless brat."

"Ow! Meda-what?"

=====

"Ohhhh," Naruto said, and now his eyes were wide. "But... but... perverted old man, Sakura-chan's breasts aren't very large at all..."

"Then she's probably a fairly kind-hearted woman," Jiraiya said, nodding solemnly.

"And Hinata-chan... Hinata-chan barely has any breasts at all..."

"Then she's probably wonderfully kind and thoughtful!"

Naruto screwed up his face and thought about it. "But, if that's true, why would anyone want big breasts, perverted old man?"

"Ah ha!" Jiraiya tossed off the remains of his sake and slammed the bowl to the table. "Very good! I can tell you why in one word."

"Tell me! Tell me!" Naruto slapped his hands down on the table and leaned forward, every particle concentrating.

"Aesthetics," Jiraiya proclaimed, grandly.

Silence. Naruto blinked, once. "Estha-what?"

Jiraiya buried his face in one hand and groaned.