One might wonder why Yuna would carry around a scroll that was filled with a picture of a giant all-female orgy... Well, okay, considering who we are talking about, it is not THAT weird for her to have something like this with her, but she actually had a genuine reason.
Despite being the leader of Konoha's most prominent clan, Yuna still does the occasional mission if it interests her or if someone asks for her directly.
In this case, a rather shameless person who would like to stay anonym sneakily created an S-Rank mission to... acquire... this artwork from the Land of Lightning, and since Yuna never acted as an art thief, she became curious and took the assignment.
As for people who have the knowledge, power, and skill to sneak an S-Rank mission under Tsunade's nose without being found out... well, there are really not that many in Konoha, making the culprit rather obvious.
"IMPOSSIBLE! THIS HAS TO BE A LIE!!!"
While Yuna was contemplating about her mission that was interrupted by Sasuke and Itachi's fight, Sasuke started reading the scroll Yuna gave him.
It contained a report about Itachi revealing that the Uchiha clan was going to rebel, the mission that resulted out of that in which Itachi was supposed to kill all of them preemptively, the after-mission-report and, most importantly, a statement that Itachi was only willing to do it if he was allowed to keep Sasuke alive and protected.
All of this painted a relatively clear picture of Itachi. He was a man willing to sacrifice literally anything to keep his little brother safe. No, he, in fact, DID sacrifice everything he had to do so and even cashed in a favor from Yuna to extend that protection even beyond his death.
Naturally, Sasuke couldn't believe any of that. Since the Uchiha clan massacre, he pretty much spent every waking hour hating Itachi with all his being, so there was no way he could suddenly turn those emotions around from just reading a little report.
"WHAT IS THE PURPOSE OF THIS!? WHAT DO YOU WANT TO GAIN BY LYING TO ME ABOUT ITACHI!?"
Yuna, seemingly unbothered by Sasuke's screaming, simply shrugged her shoulders in indifference.
"That's precisely the point, Sasuke. I can't gain anything from you by telling you all this. Well, it's me we are talking about, and I DO get a kick out of messing with people, but I would have made up a much more amusing story if I were to try that with you. So, the only conclusion is that everything written in that scroll is true."
"BULLSHIT!!!"
Sasuke snapped and was about to crush the scroll, but before he could do so, Yuna snatched it out of his hand.
"Easy there. As I have said, this is an original. Do you want me to waste even more time by forcing me to create an authentic fake?"
However, Sasuke was barely listening to her as he held his head in pain and was about to start hyperventilating. Naturally, he didn't believe everything written in that scroll yet, but doubts certainly started appearing. Little things during his multiple conflicts with Itachi that seemed somewhat weird started popping up in his mind. Like a little muscle twitch and the occasional glance that seemed to be filled with concern. Things he previously overlooked due to his anger.
Yuna noticed Sasuke's state and decided that now was a good point to continue the conversation, so, with a wide grin, she pushed onward.
"Well, think about it, Sasuke. Wasn't Itachi pretty weak? His punches, his speed, his jutsu. Do you really believe that someone who can defeat the whole Uchiha clan would be this weak?"
Sasuke's snapped out of his panic attack and looked at Yuna with wide-open eyes. He started thinking back on the fight, and a few things indeed seemed somewhat weird. FOr example, why could he so easily push back Itachi's fire jutsu with the same technique? Could there really be such a massive gap in skill between them? Although Sasuke was arrogant and prideful, but being able to outclass Itachi in fire jutsu to such a degree seemed weird now that he thought about it.
His Sharingan was activated the whole fight, so he had no trouble remembering even the smallest detail, so after only a short moment, he realized the point that stood out the most.
"I can understand that his eyes were bleeding due to overusing them, but why was his nose bleeding? Was Itachi sick?"
Yuna coughed awkwardly before giving Sasuke a sage-like nod.
"Indeed, Itachi was very sick."
That revelation dumbfounded Sasuke. While he fought tooth and nail to squeeze out a victory, his opponent already had a foot in the grave. However, Sasuke shook his head to get rid of idle thoughts. How and why he won against Itachi wasn't the main point right now. There were other questions to ask.
"Why? Why would he do that? What was the purpose? Why keep me alive?! Why endure the pain of his illness and fight me just to die in the end without achieving anything?!"
Yuna chuckled in amusement at Sasuke's desperate questions and resumed talking.
"You still don't get it, Sasuke? Everything he had, he sacrificed it for you; everything he did, it was all for your sake. He lived the life of a traitor who killed his whole family just so his little brother could live. Frankly, I don't like his methods, but that's beside the point. The truth is, that Itachi loved you more than anything else."
As soon as Yuna finished speaking, Sasuke's face became blank. His memories went to the gruesome day when Itachi slaughtered the Uchiha clan, but this time, instead of sneering at Sasuke in contempt, Itachi's face was twisted in grief as a stream of tears flowed out of his eyes.
Only now did all the little things he previously missed click together, and he could finally see the whole picture. Tears started flowing out of his eyes as he held his head in pain. Moments later, Sasuke shouted out his grief, and an ear-piercing roar echoes over the training field.
Yuna nodded in satisfaction, took out a mirror, and held it in front of Sasuke's lower head.
"And now, it's time to reveal why Itachi insisted on getting killed by you instead of his illness."
Sasuke heard Yuna's words and looked up in confusion, but instead of looking at Yuna, he saw his own image in a mirror. His eyes widened in shock when he saw that his Sharingan was not only activated, but it actually looked different from before.
"The Mangekyou Sharingan... I see; I got it after killing the person I loved the most... My older brother, Itachi."
Sasuke probably didn't even notice that he started calling Itachi's name more affectionate than before while he was still looking at his new eyes in bewilderment.
'What incredible power! It's like I have reached a completely different level than before. With this power...'
Sasuke's facial expression changed instantly and turned into a hatred-filled grimace.
"DIE!!! AMATERASU!!!"
Meanwhile, Yuna noticed Sasuke's change in mood and rolled her eyes.
"Very well, I will count this as the second free attempt."