Itachi actually had nightmares.
It took a while for Iruka to realise what it was - he just plain didn't sleep at appropriate hours of the day.
To be fair, Iruka had thought it was just an odd jounin quirk - or maybe just a field-operative thing, because despite everything that had happened, Iruka still was very much a Village bound chuunin, and Itachi would be days, weeks at a time in the field, his downtime in Konoha mostly spent recovering from chakra-exhaustion or injuries.
The week or so he usually took after recovery to catch up on his Clan duties, however, he'd revert to a set pattern. He slept in the early evening, would wake up sometime in the night, and stay up working or reading, and then only return to bed at dawn, if he didn't have early morning training. The very rare days he had nothing else to do in the day, he'd sleep away the afternoons between lunch and dinner, but those were few and far between.
Sasuke didn't find them odd - Ita-nii had always been like that, he'd told Iruka, always reading late at night.
But Sasuke was a field active shinobi too, gearing up to chuunin soon and his own sleep schedule was nothing like Itachi's.
In fact, it was weeks in when Iruka realised that no other shinobi except Shisui in the Clan kept Itachi's hours; he was the only one who would stay up late with Itachi, when Shisui was in the village but that was all .
He realised something was wrong when, just as Iruka was getting to sleep later that night, and leaned over Itachi to turn off the light and his yukata sleeve brushed across Itachi's face.
Itachi's hand shot up, snatching at the fabric, twisting hard to yank and nearly throw Iruka aside, snarling upright to claw at his face -
Blinked bloody red.
"Iruka-sensei," he said, in an odd, almost young voice.
(Not that Itachi wasn't young. He was still eighteen, not even anywhere near his twenties, but sometimes Iruka felt young and naive next to Itachi, after… everything. And Itachi rarely sounded eighteen.)
"I'm sorry to wake you," Iruka said, a little rattled by how fast Itachi had moved, but more concerned with the way Itachi's first reaction had been to claw at his eyes. "Was it - a nightmare?"
Itachi blinked, eyes dark red, and then they were back to their usual dark brown again. "No," he said. "Startle reflexes," he said. "I apologise. I shall get up."
Iruka knew about startle reflexes - in the field, sometimes a squad would sleep in close quarters, and they had to be careful on waking their squadmates. He understood that.
But itachi had been home for days now, something about this particular startle reflex had been .
Uchiha were always careful with their eyes, right? They had to be. But it could mean that something had happened to Itachi's eyes, once, on a mission, and he was triggered by that.
Iruka was careful about avoiding them, thereafter.
Itachi's sleep patterns were - well, his own, and Iruka would never even try to raise them in conversation.
Until one night, Iruka woke up to find Itachi asleep at his desk, room and desk lights on bright and blinding.
That couldn't be good for his eyes, especially at this time of the night, Iruka thought, and thoughtfully turned off both lamps.
He was about to wake Itachi to just, go to bed if he was sleeping, when Itachi snapped upright with a sharp strangled breath that was more gasp than scream.
In the barely visible shadows of Itachi's study, Itachi was swinging towards the table lamp, reaching, clawing, knocking off books and papers and the lamp.
It fell with a heart-stopping crash and Itachi made a tight, terrified sound and.
Iruka hurriedly snapped on the room light, and Itachi was.
Hunched over his desk, heaving for breath and - his pupils were blown wide even in the light, tomoe barely visible as they spun frantically.
Staring up at Iruka and - his mouth worked and.
No words came out.
"I'll. get a dustpan," Iruka said, after a long moment. "And a replacement lamp, Itachi-kun."
Itachi blinked slowly, almost painfully, twice, before he shut off the sharingans. "Thank you, Iruka-sensei." he said, voice dry as if he'd been screaming.
"I don't, like sleeping in the dark," Iruka said the next day, sitting on the edge of Itachi's bed.
After so many weeks, he really should be calling it theirs, even if he still had his own tiny apartment across the village.
"Oh?" Itachi said, evenly. Calmly.
He didn't look up from the book he was reading.
Itachi wasn't going to talk about it.
Maybe Iruka would never get to know the details why. "I think," he said, slowly, "I need a nightlight in the room," He said.
Itachi made a soft noise of acknowledgement.
"And some along the corridors outside," Iruka continued. "It is so dark in your house, it's impossible to see anything, I don't have your sharingans, and I keep tripping over the lintel when i go to the bathroom."
Itachi exhaled. "Ah," he said. And looked up, expression still calm as water. "Whatever you need, Iruka-sensei. I'll have those installed."
"Thank you, Itachi-kun."
Oddly enough, after those were installed, Itachi slept through the night a little more often.