A/N:- First I want to clarify where the fiction stands in the main cannon. This fanfic starts just after the Nine School Competition. Some incidents would be brought forward and some of them would be skipped.

Miyuki and Tatsuya would majorly behave the same in public but the private time would be spicy. And one more thing, Tatsuya would know about him being the son of Maya a lot sooner. Probably more than you can expect. So that also would help him give his all in the relationship he has started on impulse.

And lastly, I don't own Mahouka or any of its characters. Kudos to the creator who gave us such a masterpiece. Kanpai!

..._

'Mm...What did I...'

Sitting at the edge of a bed, Tatsuya clenched his fist in the process also wrinkling the sheet which was pressed underneath him. His face was grim more than he ever remembers. His feet were touching the ground but the turmoil in his mind was resisting him to feel any kind of sensation at the moment.

At a very early age, the age when children want nothing but to enjoy their time in the activities that adult refers useless. At that age, Tatsuya was involved in human experimentation, and the handler of such trials was none other than his biological mother. Or so he was informed.

Results were in their favor but as a side-effect, Tatsuya lost all his emotion which makes up a human and differs them from a machine.

The only person for whome he could awaken his feeling which only consisted of a sense of protectiveness was his little sister, Miyuki Shiba.

As things were going, even though he noticed the slight tease his sister loved to play on him like intentional skin exposure and such, he never thought of wavering from his principles. After all, once his relationship with Miyuki, the probable next head of Yotsuba, takes any misleads, he willingly or not, has to let go of her guardianship.

However now, not only a step but he already has crossed a huge boundary that he never thought of even turning to.

Yesterday, after the Shiba sibling returned home, they got a call from the current head of Yotsuba, Maya Yotsuba. The call was something in the sibling's expectancy as their aunt always keeps a close eye on them.

During the call, the person Miyuki refers Oba-sama, brought up the matter of the heir of the Ichijou clan, more precisely Masaki Ichijou a.k Crimson Prince.

After performing overwhelmingly in the nine-school competition and gaining the eye of mostly every spectator, Ichijou Masaki became the new most desirable prince among all Nine schools. Even though Tatsuya defeated him in the Monolith Code, Masaki's popularity was never deemed but only sore up higher.

Naturally, the dance he shared with the First High School's Ice Princess was something that got glued in most audiences' memory. After all, a Handsome Prince and an unapproachable beauty rarely could be seen together in one picture.

Maya Yotsuba was precisely fixated on that matter too. More like she was investigating Miyuki's thoughts over it. Tatsuya in all honesty believed his sister wasn't a girl who could get attracted by someone with just one meeting but the way Miyuki described the mere 7 minutes she spent with Masaki felt a little off.

She didn't speak about the dance when Tatsuya was with her alone but now in front of a person Miyuki doesn't get along with much, she was practically gossiping about her experience.

The glint of joy and the blush she had adorning her flawless face when she spoke about Masaki was something Tatsuya never thought of spectating from her. She went on and on about Masaki for a couple of minutes before Maya pulled Miyuki out of her stupor.

Tatsuya from start to end was silently watching her. Her expression, her gestures, her enthusiasm, he watched it all and found himself somewhat lost.

It was the first time since he could remember, that he felt something like this. The person who generally takes less than a blink to determine the highly consequential decision was actually struggling to identify his current feelings.

But the matter was, he didn't know how his conscious mind aroused such emotions. He was sure that no Mind Interference Magic was invoked on him. And even it was, he didn't have such the basic emotions that could be manipulated. His emotions weren't sealed nor broken he just didn't have such a thing as a resident inside.

But why did he feel such heavy emotion surging through his nerves and forcing him to do something unspeakable? He didn't want to hear anything related to Ichijou's heir anymore, especially from Miyuki.

He held such emotion for quite a long period and went back to work. Even though his fingers were continuously beating upon his terminal keypad, his mind was rummaging to find the reason why he awoke such emotion all of a sudden.

But what halted his train of thoughts and eradicated all of his reasoning was Miyuki's voice. It wasnt directed to him, the only resident inside the house but for a person living miles distant and currently on a voice call with Miyuki.

He lost it.

Something went off in his mind but before he could have evaluated his surging emotions which generally show up in figurative form, his body was already on a move.

He moved toward her room and halted for a second to listen to whether he heard was true or something really had happened to his consciousness.

But when he heard her giggling with the name 'Ichijou-san' attached to it, from the other side of the door, he let go of the last thread of his comprehensible capability and crossed the barrier between them.

The one who had vowed to always protect his little sister suddenly becomes the monster he should have protected her from. He had his way throughout the night with Miyuki. Even if it started with reluctance on her part she never rejected him.

Only one thing kept on repeating from her mouth even though she was suffering from the pain she didnt should have at this age, and that was...

'Don't regret this afterward Onii-sama.'

He didn't know whether she was threatening him or warning him so he doesn't let go of their relationship, but at that instance, he accepted everything she threw at him. Restlessly he used her and made sure that she belonged to him. Even though she was in tears he never stopped and kept on marking to whome did she belongs, who could keep her smiling, could protect her, and make her happy.

Suddenly a feeling of letting go of the accumulated desire surged through his nerves and he vent it on his precious sister.

'What have I done...' Looking at his hand which had Miyuki's teeth mark he felt a shiver from his back.

Without turning he knew Miyuki was awoken and currently was in a foul mood. After what he has done nothing less than death was worth putting up with his sins. Not even death would be enough to compensate for the deed he partook willingly.

Unfortunately, death wasn't also in his capability to accept. After all, he was a tool made for Yotsuba.

Tatsuya didn't budge from his spot and patiently waited for his punishment whatever she thought worthy to gain at least a sense of ease even if it was only for an instance. He could do anything for her happiness and if her happiness lies in a man other than him...

"Onii-sama." Suddenly a warmth spread on his back as the suppleness of something soft pressed against him. The sweet scent which was blended with his own wafted and surrounded him like a heavy blanket.

Two thin gorgeous arms which were foiled because of the teeth marks belonging to none other, wrapped around his neck as Miyuki's soft whisper blew near his face.

"Mi-Miyuki?" Her mood was ugly that's what Tatsuya could perceive but her actions didn't justify her agitation.

A soft bite on his earlobe made him even more baffled as well as her possessive embrace. She was bare naked just like he was, which resulted in direct contact with their skin. If she was unaware of her condition then Tatsuya's natural heat would have alerted her.

But the way she was clinging to him made it look like she didn't mind that at all. More like, she wanted to feel his bare body more than he did last night.

"Onii-sama, you remember what I said last night?" Her beautiful finger which was circling his left chest plate suddenly dug inside his flesh before blood started spilling after drenching the tip of her finger.

Tatsuya didn't feel much from it more like he was focused on her words more than her action. He took a deep breath before he voiced his thoughts.

"Miyuki, what happened last night-"

"I asked, do you remember my words which I was shouting at the time you were about to take my chastity?" Her dug finger attained the strength she required to move it accordingly as she raised her voice in annoyance. As Tatsuya expected she indeed was in an awful mood.

Tatsuya leaned back as he supported his back onto her front to let her do whatever she wanted with his body as a reply came not so long after.

"I do. You said not to regret what I was doing."

Answering truthfully he looked at her expression and found her displaying a smile he was unfortunately used to. Something he has faced from a woman he feared and respects the most. Until a decent year, he had witnessed such emotions overflowing out of her for him from very intimate proximity. So finding Miyuki in the same state he was startled to even notice what calligraphy he was getting designed in.

"Now tell me, my dear Onii-sama. Do you regret sleeping with Miyuki? Do you regret crossing such a line with Miyuki? Do you regret regarding Miyuki a woman as a potential partner? Tell me Onii-sama, do you regret any of it?"

Tatsuya was just studying her wavering emotions which aroused a sense of danger. He was incapable of holding such a relationship with any woman but with Miyuki, he certainly feel a lot more human. He could feel her change of emotions and what was making her so furious at the moment.

So he stuck to such feelings and answered what still was disturbing his calculative mind.

"No, I don't." Such a short answer yet it filled Miyuki's heart at peace. Her hand movement had already halted but now the trembling of her hand was vivid. She tilted her head toward him but before she could have let go of her agitation, a frown formed on her alluring face.

She wrinkled her brows slightly as a chilling aura took over her demeanor.

"Onii-sama, I do trust you more than anyone in the world but right now why do I feel you lied to me?" Tatsuya didn't answer more like he was pressed down with Miyuki's next statement.

"Well, even you have lied. Even you regret your actions. From now on, the fact that we aren't only a pair of siblings would never change. Miyuki loves Onii-sama as a brother and a man too. So even if you think you can go back to the Aniki-Imouto relationship anymore, throw it away Onii-sama. From now on Miyuki belongs to Onii-sama and Onii-sama belongs to Miyuki~"

Saying such she got out and while still being naked landed on the floor. Tatsuya still had the shame that he turned his head to not look at her current appearance.

Helplessly he let go of a sigh as a sensation of failure brother as well as a man washed over him. In that overwhelming sense of depression, he leaned his face down before another sigh left his lips.

His chest was still bleeding but the more meaningful thing to gawk at was something else. In clear letters, a simple word was imprinted on him to make it look like he now belongs to his Imouto not emotionally but physically too.

The beautiful name of the very beautiful person he has ever come across to.

みゆき

..._

A/N: I hope you guys liked it.