Iruka Mentions in the Kakashi Retsuden Novel
"The sleep chakra point, a technique he had learned directly from Iruka, the principal of the ninja academy. When Kakashi mentioned in conversation that he had trouble sleeping sometimes, Iruka had taught him a secret jutsu for inducing restful sleep. The sticking point, through, was that it was hard to hit the spot on yourself, given the chakra point was on the back of the neck."
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Kakashi confides in Iruka, and Iruka is more than willing to conduct some private lessons for the Rokudaime.
"Before he became Hokage, Kakashi had only known how to kill people. He had methods of capturing people without killing them, but they all invovled pain and torture. But as time wore on and the country grew stable, the shinobi principle of capture without killing had taken favor. And it was none other than the Sixth Hokage himself who struggled with how to write the guidelines for this new no-kill capture policy. He'd discussed it with Iruka, the principal of the academy at the time, and he had laughed. Kakashi remembered every single word of what he said.
(Iruka) "It's ok. It might not look it, but we do more than just teach students at the academy. We've saved jutsu to make an enemy fall asleep instantly or freeze them on the spot. Everything from old to new is right here."
Distracted by the memory of Iruka's proud face, Kakashi accidentally allowed a bit of fabric to rustle while strangling the ninth shinobi."
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What can I say? Kakashi certainly doesn't need the Sharingan to remember Iruka's every word, his laugh and his proud (most definitely smiling) face. In fact it's so distracting he blows his cover on a dangerous infiltration mission remembering it. Yeeeesss.
Iruka is also the last major mention at the end of Kakashi's novel:
(Sarada) "I'm heading out. I got a present for Master Iruka," Sarada said, holding up a cherry pink paper bag. Strawberry Daifuku from Tami Traditional Sweets in the old city. They were widely known to be extraordinary and quickly sold out, so they were hard to get ahold of, a rare treat.
"Oh right, you're doing a homestay at Master Iruka's, right?" Kakashi said.
"Yeah!" Sarada nodded happily. "Cuz Mom and Dad are away on a long mission. Master Iruka's an amazing cook. He's teaching me all kinds of stuff. It's loads of fun."
"Ohh. He is pretty skilled."
Iruka was a longtime bachelor like Kakashi, but unlike Kakashi, who paid little attention to his personal life to start with, Iruka kept a neat home. In contrast with the desk of the Sixth Hokage, which was always covered with scattered papers and documents, the principal's office at the academy was famously neat and tidy.
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Kakashi knows Iruka's a skilled cook. He knows Iruka keeps a neat home. (I wonder why) Kakashi's also recently developed a bit of an onsen interest. (Iruka's official data book entry lists onsens as his hobby.) They are both confirmed bachelors. Nice.
