Disclaimer: Do a barrel roll!
AN: Yes, I'm completely serious. This is an (read: my) explanation of just why it's called a "Bingo Book." It's also proof that I have far too much time on my hands. Enjoy!
The tranquility of the training ground and Team Seven's lunch break was shattered by a resounding "What?!" Its source, a scrappy genin dressed in blinding orange, stood, pointing dramatically at his squad's leader.
"No way! You've got to be kidding, Kakashi! Tell us the real reason!" The rest of Team Seven agreed with Naruto, though with fewer decibels. As for Kakashi, he was just sorry he had even paid attention to the genin's question.
"That is the reason, Naruto. That's why it's called a Bingo Book." It was taking all his self control to keep from strangling Konoha's number one knucklehead ninja, or the more painful option, bashing his own head against the nearest tree until unconscious to escape the questioning. "Ask any jonin and you'll get the same answer. In the Hokage's keeping are a number of bingo boards that, instead of numbers, have the faces of criminals listed in the bingo books painted in each square. Once a criminal is captured or killed, their face is crossed off the board and the name of the shinobi who completed the mission is recorded. If a shinobi manages to complete a row on any of the boards, they are paid a bonus bounty."
This time his explanation was greeted with silence as the genin mulled the information over. Sakura and Naruto seemed to be at a loss for words, Kakashi hoped that they would just accept what he told them. It was the truth after all. Sasuke, however, had no such problem. Shifting slightly in his place, he broke the silence with a disdainful scoff.
"You jonin must be easily amused." His slightly disinterested, slightly sarcastic remark seemed to break his teammates from their wordless stupor and, much to Kakashi's dismay, they joined in.
"Tell me about it..." Sakura rolled her eyes, sounding more like Ino than she would ever admit. "Genin don't need to play bingo with human lives to keep busy."
"Yeah! We just do our jobs, usually chasing after stuff..." Naruto finished, gulping down the last of his lunch and looking a little disheartened. Partly because the food was gone, and partly because of the thought of all the low-level missions they had been going on lately.
Kakashi saw the remark as an excellent tool to wrench his students' focus back to the work at hand: their training. He pulled out his book, the most current volume of Make-Out Paradise available, and started to read with a nonchalant air, disguising his sinister plot as an offhand remark.
"Speaking of chasing, Naruto... I heard the Daimyo's Wife's cat got loose again." It was a lie, but the look of pure horror pasted across each genin's face told Kakashi that his plan was going to work perfectly. "Since it seems we're finished with lunch and you three are mature enough to simply do the jobs you're assigned, I thought we might skip the rest of our training and go accept the mission to recapture that wayward cat." Peeking over the top of his novel, Kakashi could clearly see his students had been pushed into fight or flight mode and were desperately searching for possible escape routes.
"Ah, wait Kakashi! We um, we can't just go running off on a mission. We've really got to train!" Naruto, the one who usually got hurt the most on these feline-related missions, looked about ready to beg if Kakashi didn't relent. Sakura and Sasuke didn't look much better, but then no ninja likes to chase household pets through hazardous woods for hours on end.
"Y-yeah Kakashi, we haven't actually trained together in a long time." Sakura's voice shook as she spoke. "We really need to practice."
Sasuke didn't say a word, but the lone bead of sweat running down his forehead and small facial tic spoke volumes.
Satisfied that the three genin were suitably terrified and the subject of bingo was far from their minds, Kakashi smiled under his mask and set aside his book. The plan went exactly a he expected, now it was time to play the part of the gracious and understanding teacher.
"All right then, let's get going. We have lots of training to do."
AN: The lesson here? Jonin are sneaky and manipulative. Or is it that genin are just easily fooled? Either way, bingo is a ninja favorite. (And I'm well aware that there's likely some obscure source that gives a canon explaination of why it's called a Bingo Book, but I don't remember or know of it. I'm usually a stickler for canon, but this time around I can honestly say I don't care. I like my version better. It gives the jounin-level shinobi more of a sense of humor.)