During the night Naruto was out to see if some stupid clan had thrown away old scrolls again. Really, for all the talks about keeping clan jutsus a secret, they were pretty lax with the scrolls that had their secret jutsu and sometimes training techniques in them.
Whenever the scrolls got too old to be used anymore the clans had somebody copy the content of the scrolls and then threw away the old ones. Instead of burning them directly, they threw them into the trash. Naruto, ever the opportunist, regularly searched the trashcans the day before the trash was collected and destroyed.
That was the day the clans threw away those scrolls. Over the years since he had started to do this to even out the advantage the clan ninjas had on him, he had collected quite a lot of scrolls.
Naruto now knew perfectly how to fight members of all clans in Konoha. He even could use the gentle fist. It was fairly easy with his vast knowledge of anatomy.
While he couldn't see the chakra network without the byakugan, a chakra strike to a vital organ or a muscle was still fatal for an opponent. And it added to his unpredictable taijutsu. After all, nobody would expect a Non-Hyuga to know gentle fist.
But before he could do his little raid, he got suspicious of a figure that left the Hokage Tower with a big scroll on his back. He decided to investigate. He made a shadow clone to continue his trash raid; there was no reason to not do both after all.
He stayed in the shadows, his chakra suppressed to not alert the man he followed to his presence. Once he reached a clearing in the forest, the man stopped to gather his breath.
"That went well. It would have been better if I could have blamed the demon brat, but with the brat passing the exams that plan got blown up." He mumbled.
Naruto recognized the voice as the one of Mizuki, his teacher at the academy. So he had planned to trick him into stealing the scroll he had with him. It had to be important that he would risk the theft from the Hokage Tower. Naruto sneaked closer and positioned himself over Mizuki, ready to take him out.
...
While Naruto was tailing Mizuki the Hokage noticed that the Forbidden Scroll had been stolen and raised the alarm. Many were accusing Naruto, but an ANBU informed them that Naruto was sleeping in his bed at home. The Hokage sent his ninja out to find the thief and bring back the scroll.
Iruka who had taken to search in the forest west of Konoha was really surprised to find Mizuki with the scroll. Never would he have thought his old friend would do something like this. Iruka didn't notice Naruto in the tree.
"Mizuki, what are you doing?" He shouted enraged.
"Oh, look who found me, Iruka. What does it look like? I am taking the scroll to become more powerful than I could ever become in this shitty village.
Once I have learned the jutsus in it, I will be invincible. Nobody will be able to stop me and I will then sell it to the highest bidder." He said. "Sadly I can't have you tell my little secret, so you sadly have to die."
Mizuki attacked Iruka with a windmill shuriken, which Iruka managed to dodge. The two started on taijutsu, where Iruka was definitely at a disadvantage.
"Oh, didn't the good little teacher keep up with his taijutsu training well enough?" Mizuki mocked Iruka when he kicked him in the rips and against a tree.
Then he threw the next windmill shuriken at Iruka, who couldn't get up fast enough. But before the shuriken could hit, it was intercepted by a dark figure.
Naruto had seen and heard enough to decide he wanted to thwart Mizuki's plans. And with his disguise there was no risk of being identified. Mizuki was shocked to see his attack didn't hit.
"Who the hell are you? What do you want?" He yelled at Naruto.
"I hate traitors with a passion. That's all." Naruto said and threw the windmill shuriken he had caught before it could hit Iruka back at Mizuki with a lot more speed than it had had before. Mizuki dodged the weapon.
"Hah, you missed." He mocked only to be hit from behind and feel the pain from being pierced by his own weapon.
"No, I didn't." Naruto calmly said, holding the end of a thread of ninja wire in his hand, which he had quickly tied to the windmill shuriken and therefore been able to pull the weapon back on a new course.
He took out a senbon covered in a paralysing poison and hit Mizuki in the neck with it. He passed out soon after from the blood loss. Iruka managed to get up, only holding his side a bit.
"Thank you for the help." He said. "You saved my life."
"You're welcome. I think it would be best to get the scroll back to the Hokage. Can you walk on your own?" Naruto asked.
"Yes, I think so. Only a few bruises, nothing serious." He said. "By the way, who are you; I don't think I have seen you in the village before."
"That's a secret. If you want to have a name, you can call me Dark Phoenix. That's my codename." Naruto said.
He had decided long ago that he would use that codename if he ever was seen. It was his best shot to be left alone if nobody knew what he could do. Dark Phoenix would be thought of as a secret operative of the Hokage and nobody would make the connection to Naruto Uzumaki, the demon brat.
"Oh, I understand." Iruka said.
In a ninja village people with codenames were nothing special. Hell, the ANBU only operated that way. While Dark Phoenix seemed to be really young, there had been others that strong at his age. Naruto bound Mizuki with wire and asked Iruka if he could carry him as he had the height advantage.
They walked back to the village not being in a hurry after the culprit was caught and knocked out. And it would be easier on Iruka's bruises. Iruka was carrying Mizuki's knocked out body and Naruto had the scroll.
When Iruka was briefly looking in another direction, Naruto quickly switched places with a previously made shadow clone. There was no chance he would pass the opportunity to copy the jutsus from the scroll.
It wouldn't take long. Because of his sealing training Naruto could write really fast. Just when they were getting to the edge of the forest, Naruto switched back. Nobody would ever know that he now had the forbidden jutsus of the village.