This is one idea I've had for a very long time. I love the twins, and I really love these little tidbits we get of Saizo. The idea of Kaze waking him roughly really started this for me.
It was due to Queen Mikoto's protection that Hoshido had hardly been touched by war. Battles were fought away from the capital, with many just going about their regular lives with little to interest them. Until one day, a flurry of excitement had enveloped the people as Prince Corrin had finally been returned home from his long captivity in Nohr. But not everyone was excited.
It was Saizo's duty to serve Lord Ryoma, the future king of Hoshido. Lord Ryoma loved his siblings, even going to the point of making sure Azura, a princess of Nohr stolen in an attempt to trade her safe return for Corrin's years ago, was treated no differently. That alone had been challenging for Saizo to handle. He mistrusted her, and he knew he could lose his head for doing just that. And now that Prince Corrin was around, that was double his distrust. He knew he could not voice his suspicions, but he would observe the two of them along with carrying out the rest of his duties.
It was draining.
There were nights that he had to be reminded to sleep. He rarely liked to go to bed before Lord Ryoma, in order to ensure his safety. He tried not to make his presence known, but even he could not completely cover a yawn or two. On one particular night, try as he might, the ninja could not stop yawning.
It was after the fourth or fifth yawn that Ryoma looked at him and said, "I shouldn't have to order you to sleep, Saizo."
"Forgive me - " Saizo began, but he was cut off.
"Just go to bed. You can't do your duties if you're asleep on your feet.
Saizo bowed and left the future king of Hoshido. He did not want to, but was there little to object. Ryoma did have a point, though it shamed him to be forced to go to bed.
As he walked to his room, he still swept the hall with his good eye. Just because he had to retire for the night did not mean he could, or should, stop making sure there were no hidden daggers lurking about. He found no one as he always did, but it hurt no one when he was wary. Others would scoff or openly mock his protective behavior, but he took his work very seriously.
He even checked his own room, sparsely decorated as it was, before going to bed. As one entered his room, they would assume there was little space to hide. But Saizo knew, from experience himself, that a ninja could hide just about wherever he or she chose to. That night, as he did every night, he checked under the bed and in his trunk. Satisfied, he sank into bed and was asleep in an instant.
Almost an hour later, after Saizo was in a deep sleep, the door to his room slid open. The other ninja slipped silently into Saizo's room. He had learned from previous episodes with Saizo that it was best to be able to flee as quickly as he could. For a moment, he thought of leaving. Saizo was fast asleep, and he rarely slept so peacefully.
Kaze decided against leaving and pounced. "Saizo!" he shouted as his knees landed right next to his older brother. He seized Saizo's shoulders and shook him roughly.
Saizo grunted as his twin jumped onto his bed, nearly knocking him off it. Ever since the two of them were little, Kaze enjoyed roughly waking him at any opportunity. He struggled for a moment against his sheets as Kaze's laughter filled the room. It was like being home again, but it was not a young Kaze unable to sleep who woke him. It was a fully grown Kaze who laughed as he untangled himself.
"I - was trying - to sleep!" Saizo snarled.
Kaze started to speak, but Saizo was not in the mood to listen to any explanation. He knew there was none. Kaze was just being himself. Saizo lunged across the bed. Kaze avoided him and darted towards the open door. Saizo flung the sheets aside, leaped from the bed, and raced after his younger twin. Kaze's laughter echoed in the hall as Saizo hurried to catch up.
Kaze cut a corner swiftly, but Saizo was right behind him. In his haste to catch Kaze, Saizo knocked over a pedestal, and a vase that rested on top of it. Both hit the floor with a crash. It was not the first thing the twin brothers had destroyed in the castle. Nor would it be the last.
Kaze leaped over a dog that had fallen asleep in the middle of the hall. He did not even ruffle the animal's fur as he passed. Saizo reached out; his hand brushed against his brother's arm before Kaze ducked and rolled away. He swerved and took a sharp left, hoping to throw Saizo for a moment or two. If he could make it outside, he could get away from Saizo. At least for a little while. Saizo always made sure to get his revenge if Kaze woke him. There was really no escaping him.
The two of them darted past the throne room. Princes Ryoma and Corrin both stuck their heads out in confusion. Ryoma realized what was happening and started to laugh. "Should we do something?" Corrin asked out of concern.
"They'll work it out."
"But - " Corrin winced as another distance crash was heard, followed by the tinkling of shattered glass. "Saizo might really hurt Kaze." Saizo shouted at Kaze; what he said neither prince could understand. But they could still faintly hear Kaze's laughter.
"Perhaps you're right," Ryoma told his brother, "if only for the sake of the palace."
"You aren't worried about Kaze?" Corrin asked as they followed the sounds of the two ninjas.
"Saizo won't kill his own brother."
The thought had occurred to Saizo as he continued his attempt to catch his sibling. Ryoma was right. He would never actually do it; he'd never hurt Kaze unless he had to. He was angry at being roused from sleep, and so the thought had crossed his mind. As Kaze came close to exiting the castle, Saizo took the chance and tackled his little brother. The brothers flew out the door and tumbled down a short set of stairs. Saizo landed on Kaze, pinning him down on his side. Kaze gasped as the air was knocked from his lungs.
"Why did you do that?" Saizo demanded.
"I wanted to." Kaze's cheek was pressed against the ground, his right eye squinted shut. He squirmed under Saizo, but his arms were pinned and he could not move. "I haven't seen you in some time."
"Hmm." Saizo narrowed his good eye and stared at Kaze. It was an odd way of showing affection or asking for his attention, if either of those was what Kaze truly wanted. He had assumed it was simply to be annoying. He released his grip and rose to his feet. Kaze sat up and rubbed his arm.
"Thank you," he said softly. "You know, you haven't said anything to me since I returned from Nohr."
Saizo blinked in confusion, his face impassive. He had spoken to his brother, but then he realized what Kaze meant. "I'm... glad you weren't... executed by the Nohrians," he mumbled.
A smile formed on Kaze's face. It was a lot more than he expected of Saizo, who sometimes struggled with expressing deeper meaning to his words. "Thank you, brother, I'm glad to return with my head attached as well." Saizo, who had turned away from Kaze and mumbled about going back to bed, did not see the smirk on his brother's face. He seized Saizo from behind and began tickling his ribs.
Saizo squirmed and tried to wiggle away from his brother. He also tried to hold in his laughter. He quickly failed at both. Saizo knelt, one hand on the ground to brace himself, as Kaze's onslaught of tickling continued. "Ahaha - Ka - Kaze, stop - aha - or - or - " He covered his hand with his mouth to try to muffle his laughter. He hated being so ticklish. It was far from the attitude he tried to project for himself.
"Or what?" Kaze demanded.
"Or I'll kill you!" Saizo managed to escape his brother's grasp for a second before Kaze was on him again. He collapsed in a fit of laughter, his face nearly as red as his hair as he hid it in his arms, his body trembling with laughter.
Corrin was surprised to find a helpless Saizo under Kaze's control. The red ninja had seemed so intimating and serious. It was quite the surprised to see him in a fit of laughter. He turned to Ryoma, who was far from surprised though he did smirk at the sight. "I told you Saizo wouldn't hurt his own brother," he pointed out.
"Does... does this happen a lot?"
Ryoma's laughter joined Saizo's as he said, "More often than you think."