The first to notice the oddity was Umino Iruka.
Sandaime informed him in confidence that Naruto could never be a proper ninja ifat all, because the seal that Yondaime placed on him was slightly defective, allowing Kyuubi's chakra to permanently damage Naruto's chakra circulation system. It wasn't absolutely unsalvageable, but the very few people that could remedy it were either dead or out of village - Princess Tsunade being the only one in the latter's case. Iruka thought it was cruel to let Naruto try fruitlessly to be a ninja, but he also wasn't sure if it was less bad idea to tell Naruto that he could never be a ninja, let alone Hokage. Sandaime and Iruka was not sure how to approach it without breaking the child's heart too much.
But at the same time, Iruka knew Naruto was persistent.
So, when he saw Naruto barely paying attention in class and shrugged after being scolded, Iruka's instinct told him that something was not right with him.
"Naruto! You will come to my office after the class!"
"Okay," said Naruto. There were deep dark bags below his usually lively, but now withering, blue eyes.
After the class, Iruka pulled away Naruto to his office - most teachers went out for lunch - and sat him down. "Naruto, what's wrong?"
"Nothing. I am not sick or anything," Naruto answered. His eyes avoided Iruka and kept wandering, as if avoiding something.
"No, I mean that you are not paying attentionat all.I know you are not exactly book smart, but you still used to be passionate about ninjutsu. But in last few weeks, I noticed you were paying less and less attention. You look sick, too. What's going on?"
Naruto maintained his silence. Iruka patiently waited for his answer. "I am just...really tired."
"Naruto-"
"No, sensei. I just need to have more rests, I haven't been sleeping right these days," Naruto rubbed his eyes.
"Naruto, I will take you to a doctor-"
"NO!"
Naruto screamed so loudly that Iruka jumped a bit. Never had Iruka seen Naruto shout so unexpectedly, gathered in Naruto's terrified eyes. "Please, sensei, I really don't want to go to the hospital. I don't want to."
"Naruto..." Iruka then took Naruto to a private room, where teachers took students to discuss matters that they deemed too sensitive for the students or the teachers. A few teachers stared at them in an intense curiosity - what made that troublemaker so frightened?
"Naruto, listen," Iruka smiled as gently as he could to console the boy who was so shaken by something that he didn't understand yet. "I care about you. I don't want you to see you in such a terrible state. I knew you for years, and not even Jonins scare you this much. Did someone do...things that made you uncomfortable at the hospital?"
Naruto shook his head. He licked his dry lips. "No...I mean, nurses are not the nicest, but that's not the reason."
"Then what is it?"
"...Will you trust me?"
"Naruto, please trust me that I will trust you." Iruka hugged Naruto tightly, who to his relief, reciprocated, though weakly.
"Iruka sensei, would you rather be blind if it meant you didn't have to see things that others can't?" .
Hiruzen knew that he was a very imperfect guardian for Naruto.
As a leader of the village, he could not show favoritism or any special attention to anyone, even for the son of the late fourth Hokage. It would cause unwanted rumors and conspiracies that would further harm those he wanted to protect, and that was especially true for Naruto. Hiruzen wished that he could spend more money on Naruto, but Naruto's assets were tightly sealed until he would mature, and not even Hiruzen could override it. All he could do is to give him basic support and constant watches through his ANBU and the telescope jutsu through his crystal ball. It killed him that he could not punish Danzo for leaking Naruto's jinchuuriki status.
Recently, he noticed Naruto's changes in demeanors. The boisterous and attention seeking boy became fidgety, withdrawn, and sometimes scared of his own shadow in a quite literal sense. He constantly looked around with paranoid expressions. He even cried alone when there was no one else. Sometimes, he would run away from something that neither he nor ANBU could detect. Eventually, Hiruzen thought that Naruto may have had some kind of mental damages, causing him to see things that weren't there.
That was until Iruka, who never demanded anything, begged to talk to him. When Hiruzen saw Iruka, Naruto was with him, tears and snots on his face.
At first, he thought Iruka perhaps bought Naruto's words too literally, but he still listened to Naruto's plea. Naruto did not know why and how, but he started seeing things, mostly dead people wandering around and doing seemingly nonsensical things. Hiruzen pitied the boy - a schizophrenia was no laughing matter, even for the most hardenedninjas. Ninjas would see gruesome things in their careers, so the hallucinations that begot from the deepest trauma would sometimes drive them into suicides.
Then, Naruto described something that he should have not known at all.
"The white haired man with a ponytail sometimes stares into the apartment complex near downtown...and he follows another guy that looks at him for an hour."
Hiruzen wanted to throw up when Naruto accurately described Sakumo Hatake. The man who was dishonored for failing his mission...he still wandered in a living plane. Was it the stigma and resentment that bound him? Or was it his concern for Kakashi?
Sandaime pushed away one of his many lifelong regrets that he wanted to bury in his memory. Now was not the time to worry about the dead. What mattered was to save Naruto from his own visions, lest he would go insane and hurt himself.
"Lord Hokage...?" Iruka asked, concerned at Hiruzen's unusually sickly expression.
"Iruka. I have a very important sole mission for you, " Hiruzen ordered grimly, "Go to the Fox Sanctum in Madogakure and ask for the priest Mahito... What we have here is far beyond our capabilities."