A sadistic Princess should have a sadistic knight.

Plan.

Takasugi eyed the icy waves that crashed hopelessly against the formidable wood of their ship, taking a drag from his pipe.
"Takasugi-sama~" squealed the forever-promiscuous Kijima Matako, latching possessively onto the arm of Takasugi.
     "That's not the boss, Matako, it's Henpeita. The boss is in his office," said Kawakami Bansai, materializing from behind her.
     Startled, the blonde looked up at the masqueraded Takechi Henpeita, who in turn removed his uncanny disguise to reveal absent doe-eyes and emotionless visage. "Wah! No way! I wanna see Takasugi-sama! Isn't he glad I'm back?"
     "Bansai."
     "Takasugi-sama!!!" Exclaimed Matako, sprinting towards him with outstretched arms.
     Takasugi halted her with his palm and roughly pushed her away. "I don't have time for that, Matako. Bansai."
     "Yes, sir," Bansai acknowledged reverently.
     "We have much to discuss."
Kamui leaped from the roof of the sail's post and landed flat-footed.
     "Y'know the officer-chan I told you about in my letter?" Kamui asked, interrupting Takasugi's speech.
     "Y-Yes."
     "Apparently, he's quite strong. Strong enough to knock the wind out of Takasugi-chan and escape."
There was a horrible silence.
     Takasugi exhaled wisps of smoke. "I was only caught off guard," he said sullenly. "Who asked you to come down here?"
"I don't need someone to call me," Kamui responded smilingly.
"Nevermind that, then," Takasugi proceeded, "the Yato Princess' guard precluded the brainwashing. He f*cking-"
"Watch your language, Takasugi-chan~"
The others sharply glanced at Kamui, bewilderment etched on their faces. But Takasugi only clicked his tongue in retaliation to the admonishment. Disturbed, they steadied their gazes on their leader again.
"He stood up and left. Took our spare boat and just sailed away. It was astonishing." Another drag. "What do you suggest we do, Bansai?"
He pondered this. "I say we survey them more. We'll send Henpeita to spy on them for a bit. Find cracks in their King, their army, and that knight. We'll create a plan according to the results and execute it cautiously-"
"Boooooooooooooooring," gawked Kamui.
They glanced at him sharply.
"What?" Takasugi demanded lowly.
"It's awful, that plan. It'll take too long. They'll find us first. I say-"
"We're not doing what you say," he said acidly.
"I say we saunter over at night," Kamui continued, "Casually. They don't know who I am, so I'll write a letter saying I'd like to be imouto-chan's tutor. Of course, they'll be wary of my presence so most of his puny army will be keeping an eye out for me. My appearance is conspicuous, no? You guys will blend in fine."
Matako spoke up, "What, so you're sayin' is that most of the work is on ya?"
"No. You guys will swoop in and kill everyone in sight. Unless it's the princess, you shouldn't let anyone escape alive," he turned to Henpeita, "you. I've forgotten your name, but can you make a disguise for me?"
"I can," he said tersely.
Takasugi gripped Kamui's shoulder hard. "Who made you the captain? Do you know how risky this idiotic plan of yours is?"
"Nope. Not until I try it."
Bansai straightened his glasses and leaned against the cabin, gazing shrewdly at Kamui.
...
Kagura briskly walked down the corridor, ruminating on Sougo's motives. When had his apparent feelings for her manifest? Why is it that he's declaring them now? What-
     "Oh, Hime."
     She jumped and looked up to witness the infamous contemptuous smirk plastered on Okita Sougo's face. He bent down to whisper in her ear, "are you thinking about me?"
     She protested mechanically, humiliated and conspicuously red. She held her hands up as if she was being asked to, he then realized: ah, she doesn't want me to come closer. This earned a rare chuckle from his originally placid disposition. "What?" She said, her voice unstable, "What's so funny, you-"
He flicked her forehead and proceeded to walk passed her.
     "I win."
He disappeared before she could ask what he meant.
...
    "Tsukki, look at this."
Tsukuyo materialized from Sarutobi's veranda, Otae and Kyuubei staring warily at the dusty-brown paper of a letter.
     "What is it?" She asked.
     "I was on patrol and this strange person handed it to me. Said it was for Gintoki," Kyuubei explained without looking up.
     "Tsukki, I don't trust this," Otae said worriedly, glancing at the blonde.
     "You don't suppose the mysterious author is seriously intent on attacking us?" Sarutobi asked, her tone far from the ebullience she ordinarily provides.
     "Here let me read it," Tsukuyo said. She sat down next to her friends and they demurred for a bit before handing her the paper. She rose a golden brow at this. Cool amulet gems read each word aloud with a shocking amount of calmness.
     "Dear King,
I am writing to you because I am angry. You stole my dear little sister and called her your daughter. So, without an ounce of regret within me, I shall conduct an attack on your castle. I will kill everyone and anyone until I retrieve who I am looking for.
Tootle-loo,
Kamui."
The room's temperature noticeably dropped, as the queen peered emotionlessly down at every inky black character, as though transferring them deep into her memory. The others waited, nervously, for her to say something. She was trembling, and her white skin paled further into some form of a solemn apparition.
     "I..."
     Sarutobi was quick to interject. "Tsukki, we're sorry, we shouldn't have shown it to you."
    "No, it's... I'll be alright. Excuse me, I'll go inform Gintoki."
They gently, but forcefully pulled her down.
     "Tsukki. Please don't. I'll tell Zenzo to, just breathe. Kagura-chan will be fine. We have a good army. And you're strong yourself."
     Kyuubei nodded emphatically, "We will protect Kagura. No matter what."
Otae drew her into her arms and Tsukuyo lost all of her composure and sobbed into her shoulder. They were all ashen-faced and had a very strong loathing for whomever wrote that nasty letter.
...
Takasugi puffed on his pipe as he entered groggily into his office. Not to his surprise, Kamui sitting at his desk(in which the other crew members were told firmly that that was forbidden).
     "Kamui, did you send it?" He said evenly.
The vermillion-haired man grinned and winked at him, looking at the window and pointing proudly at the bird that soared far into the vastness of the forest adjacent to their ship.
     Takasugi narrowed his eyes. "I hope you wrote that properly, or have at least gotten it revised by Bansai."
     Kamui shook his head pleasantly. "I show no remorse for the people who stole my sister."
     Takasugi snorted, "you should be more angry at your father. Wasn't he the one who-"
     Kamui's sudden rage quelled him: "Don't bring him up ever again. If you do, I will take that pipe and take your one good eye out with it. I could very easily end your life, and you know it."
All the coal-locked male could do was heave an incredulous sigh. Though he shall never admit it, Kamui was stronger than him, and he can kill him. And that was frightening.