As he ate breakfast while watching

As he ate breakfast while watching the morning news, Tatsuya noticed that he was unconsciously nodding along and hurriedly stopped his head motions. Fortunately, Miyuki’s eyes were drawn to the television, so she remained oblivious to Tatsuya’s odd movements.
"Mechanical failure? But I didn’t see any forecast regarding hurricanes or thick fog."
Miyuki’s skepticism arose from the news that a small American naval vessel drifted within Japanese territorial waters.
"It’s hard to imagine that machines would have such a large breakdown, so it probably has something to do with the motor. In this age of automated machinery, the chance that this is caused by human failure while moving in the wrong direction is slim."
Seeing the pose his sister struck as she simply(?) accepted his word as truth while nodding along, he couldn’t help but feel that his soul was being corrupted. –Of course, Tatsuya was self-aware enough to know that was nothing more than a misconception.
On the other hand……
(Even if this is Oba-ue’s direct order, the execution speed is simply too quick.)
Based on the time that the drifting vessel had been taken under "protection" and cross referenced against the time Tatsuya contacted Hayama, forget half a day, the entire episode from attack to clean-up was completed in barely half that time.
In other words, they were currently embroiled in secret warfare while their fighting strength was highly restricted, but their opponent was a nation’s professional army. This was no militia found in small developing countries, but most likely the elite of the elite from a major superpower.
No matter how capable the Yotsuba agents were, this was an unbelievable operation tempo.
In short,
(By the time I made contact, they had already distributed their assets.)
In regards to exactly what their plans were, that he was not privy to. Maybe this was a natural coincidence, or perhaps they had planned on not interfering in the first place.
Nor was it impossible that they simply wanted to see Tatsuya bow down to them and request for aid.
(Regardless of what it is, it’s not like I feel like I owe them anything.)
No matter what the background was, Tatsuya was satisfied so long as the end result was moving in the positive direction.

Miyuki intentionally portrayed her agreement to the motor malfunction explanation while she sneaked a peek at her brother’s visage.
Her brother didn’t seem to notice anything out of the ordinary from her.
While small motions that misled her brother strained her, she also wanted to keep a few things from her brother at times.
Miyuki deposited the utensils and dinnerware in the kitchen and left the cleanup to the HAR (Home Automation Robot) before heading upstairs to her room to change.
Standing in front of the mirror, Miyuki gave a small sigh.
Miyuki didn’t even need to watch the news to know something was afoot.
After Tatsuya left for his morning training after breakfast as usual, Miyuki received a phone call from Maya.
The contents informed her that "the USNA troops threatening Tatsuya’s surroundings have been dealt with."
Still, Miyuki remained unaware of which specific members of the Yotsuba Family conducted the operation. Thus, the only person to whom Miyuki conveyed her thanks was Maya. Despite knowing that these were methods to monitor her, Miyuki was genuinely grateful.
Additionally, Miyuki requested that Maya, who typically did not look at her brother or her with favor, to keep all of this from Tatsuya.
(How sly of me…… If Onii-sama knew the truth about this, then he would think that I’m a terrible girl……)
On one hand, Miyuki wished to prevent Tatsuya thinking of her as a dolt.
On the other hand, she simultaneously tried her utmost to ensure Tatsuya didn’t view her as a smart child.
From the bottom of her heart, Miyuki didn’t want to weigh her brother down.
Yet at the same time, the one thing she absolutely abhorred was for her brother to believe "my little sister doesn’t need me anymore".
Once she became the head of the Yotsuba Family and was fully independent…… Once he came to that conclusion, her brother may leave her side.
Even if he wasn’t leaving, he would probably still keep his distance.
That was the nightmare that constantly tormented Miyuki.
Miyuki and Tatsuya were siblings by blood.
As she grew older, leaving her brother was a matter of course - just as he would naturally grow apart from his sister.
Miyuki also understood that one day she must marry.
She would be forced to accept someone other than her brother as her husband.
Though this was against Miyuki’s wishes, society and this country called Japan would never allow her not to do this, so long as she was a talented Magician with hereditary genes boasting powerful magical qualities.
This was not something far off in the distant future, but something looming rather closely.
In the modern age, Magicians were required to marry early. This was especially the case for female Magicians, so that they could marry quickly and bear children. The reason behind this was that the sooner a Magician was born generation-wise, the greater the tendency for him or her to wield innately powerful magic. Scientists referred to this as "magic seeping into hereditary genes". The differences between the greatest Magicians of each generation weren’t obvious, but the average power level was on the rise. Their parents’ generation surpassed their grandparents’ generation, just as they too surpassed their parents. While this would level off sooner or later, everyone was still bound by the overwhelming urge to bring forth the next generation as quickly as possible.
It wasn’t strange for female students who applied for magical universities to suddenly drop out to raise children.
Mutations with unstable life expectancies were not under this restriction, but even now, well into the second or third generations, there was still a duty in the eyes of the public to bear children at a young age. Their mother marrying late and their aunt who maintained her steadfast resolve to remain single were both exceptions, accepted only because of inescapable physical reasons.
Miyuki was the picture of perfect health, so none of those reasons applied.
Not to mention, she was seen as the next head of the Yotsuba Family, a bearer of exceptional genes.
In reality, she wouldn’t do anything of that nature with any boy save her brother. These were Miyuki’s true feelings. No, the real truth of the matter was that she detested all the other boys except for Tatsuya.
It wasn’t a biological issue, so something like dancing was still acceptable. However, in Miyuki’s heart, the only who was allowed to touch her was Tatsuya. The only one who could do as he wished with her was Tatsuya alone.
The reflection in the mirror was that of herself clad in her underwear. As she looked upon herself, Miyuki couldn’t help but think. These fingers and this hair, lips, bosom, the secret places that no one was allowed to see, everything was available for Tatsuya to touch if he willed it. If it was Tatsuya, she was willing to do anything.
—No matter if it was her body or heart, everything that she was belonged to Onii-sama—
This was Miyuki’s truth, a wish that came from the bottom of her heart akin to prayer.
Yet, Miyuki also knew that these feelings would never come to pass.
That was what she thought.
(Even if I’m just a shameful little sister…… No, it would be even better if I seem like an unreliable, shameful little sister. If this will allow me to stay by Onii-sama’s side forever……)
As she thought this, she also worked hard to ensure she was not resented by Tatsuya.
All of this summed up the conundrum Miyuki was faced with.