A sadistic Princess should have a sadistic knight.

Concealed.

Sougo awoke. His arms were wrapped tightly about an unspecified object. And although he had not an inkling of who or what it was, it was emanating wonderful heat. He snuggled closer to it. Until a voice eerily recognizable groaned in front of him.
"Mmph. Sougo..."
Before he could register his thoughts, his arms unravelled and snaked back to his sides, and he shot up just as quickly. His head spinning nauseatingly from the effects of his swift movements, he massaged calloused fingers into his forehead to quell the pounding. With his headache slightly subsided, he returned his attention to the princess in his bed. The iridescent rainbow reflected off of her pale skin, as if her being was a translucent angel that could deteriorate at any given time. Long vermillion tresses fanned out beautifully along his pillows like an aristocratic fan.
"Hime," he called quietly.
She shifted uncomfortably, momentarily opening her eyes and fluttering long lashes, only to delve back into the abyss of sleep. He grunted in annoyance.
"My head'll get chopped off because of you," he warned, trailing gentle jabs along her slender neck.
She shifted again and swatted at his hand. He chuckled.
     "Kagura.."
She stirred.
"Did you call me without honourifics?"
For his own entertainment, he thought of what would transpire had he said yes. "No."
"Oh."
She rubbed the drowsiness from her eyes, sitting up fully and blinking away the final remnants of sleepiness. He eyed her with no look of impatience.
"You should go to your own room and get in bed. I'll get severely punished if I'm caught with you."
He dissimulated the thought of how they'd reprimand him if they found the princess had wandered around the castle at dangerous times, stayed in a man's room, and slept in his bed. His skin prickled. Of course, his placid features suggested he wasn't uncomfortable with the current situation.
"Don't be a coward. I'm going to take my time. Think of it as revenge for kissing me."
His eye twitched.
"You're seriously getting me in trouble."
"Re. Venge," she said, emphasizing each syllable with a sardonically drawn out tone.
She could really dance on his nerves sometimes. Growing tolerant to her stubbornness would be a challenge.
...
It'd be a lie if she said she wanted to leave. She haphazardly travelled across the castle at forbidden times, and even slept in her knights bedroom. But she enjoyed being where she was. The large, open doors that led out to the garden interspersed with roses, sunflowers, marigolds, Sakura trees, oak trees; young birds attempting the first flap of their wings, she felt at ease in his room. Every stress as a princess slowly ebbed away, replacing it with immense tranquility.
Her gaze casted along the other rooms, their doors slid shut, and behind those doors were people in their undisturbed sleep.
"Hime?" He asked, grazing her cheek with sinewy fingers. His handsome features held a hint of concern, and she felt heat travel to her cheeks. "Kami, you're red."
A shrill breeze flew through his hair, and she watched in awe.
     "Your hair is amazing," she blurted out inadvertently.
There was a torturous silence before he laughed- something that he's never done so intensely before.
"What the hell? You trying to seduce me? That's pretty cheap, Hime."
Her face flushed crimson. "Sh-sh-shut up! Don't mock your princess! You Sadist-"
     "OKITA-SAMA!"
Sougo hurriedly draped his quilt over him, and pushed Kagura down to the softness of his futon. His breath fanned against her cheek, and the ecstatic pounding of his heart was against her own.
     She recognized the voice. It was Otae Shimura. "Okita-sama, you must wake up, the Princess has... Has gone missing!"
Kagura squirmed uncomfortably, her breaths shortening.
     "I'll be out in five minutes. I'm without a shirt. Wait outside," Sougo said coolly, whispering 'wait' to the girl beneath him.
     "Okay." The door rattled and closed, and he removed the blanket.
He shook his head and combed his fingers through his flaxen strands.
     "What's the plan, Hime?" He asked calmly, though distress was written all over his face.
     "I'll go around the castle and say I was simply going for a morning stroll. I'll shoulder the consequences."
She stood to her full height, nearly losing her equilibrium in the process. Her legs have been still for much too long. She exited his room, her eyes snapping to the left where the other rooms stretched. Otae's door was open, an unoccupied and folded futon lying beside the doors. Cicadas buzzed endlessly as she silently rushed along the tatami mats.
...
     "That idiot. Shimura, you can enter now."
     "Yes, Okita-sama," she said urgently, sliding the door closed behind her. "Wh- what do we do?"
He contemplated this for a moment, but his mind only thought inscrutable things.
     "I'll find her. Tell the King that Him- Kagura-hime has probably gone for a stroll of solitude, and that he shouldn't worry."
     Otae looked dreadfully impatient. "But the Gin-san isn't worried! Neither is Tsukky! I'm the only one who's fretting! They don't even recognize the upcoming disasters!"
Sougo nodded. She's so worked up, she forgot to regard the king and queen formally.
     "Calm down, Shimura. I'll find her."
     "....Okita-sama."
     "Hm?"
     "Isn't that the Princess's hair ornament?"
Now it was his turn to start to worry.