OK, from this point forward, I'll do a short review and go into the Iceberg of this show.   There is a lot more than meets the eye going on.

I've watched the show, read the manga and the light novels for these answers.    Some I can quote, I'll tell you when I'm guessing.

First, let's ask the question why does Leon hate getting promoted?   There are two reasons.

The first is that the higher you rise in rank the harder it is to get married.   The book literally calls this striking range.   It appears out of the nine noble ranks, not including commoner status, you typically have to marry at your level, or only one shift up or down from that (Rank only, this rank movement ignores Upper and Lower designations). 

The higher the rank the smaller potential rate of marriage prospects.  This is why the Queen came from another realm. 

(She seems to come from a mirror version of own world's past United Kingdom [England / Scotland / Ireland]) Volume 5 Chapter 2,

But, Mylene-san’s family was at the other side of Holy Kingdom Rachelle. The holy kingdom was placed between this country and her country.

United Kingdom Repard.

It was a country that was a gathering of small countries located on a single continent. The country was unified by three houses with great influence even among all of the countries there.

Mylene-san’s family was the ruler of the country that served as the alliance leader of the united kingdom.

It was a country with a bit of circumstance and troublesome government.

After all the country was formed from small countries that only joined hand because alone they couldn’t possibly oppose the Holy Kingdom Rachelle if they launched an invasion.

A great example of this is to show the difference between the marriage prospects of Oliva the commoner and Duchess Angelica.

The nearby capital city has a population of over one million.  In appropriate age, Olivia could marry any one of somewhere between 50,000 and 100,000 young commoner males there, just in the nearby city.  She has a very large dating pool.  The total in the nation as a whole is several times that.

As a Lower Rank 2 Duchess, Angelica likely has only about 10 marriage prospects without leaving the Kingdom.  Even including the Prince and his four companions, she could not just be paired with any of the five.  After all, two of the Prince's friends are Counts (Chris and Greg) and one of the Prince's companions is only a Viscount (Jilk).  Those three are not going to be judged as a suitable matches by her mother.  That number ten includes two men (the Crown Prince Julius and Marquess Brad "the purple one") that the show already centers on.

Thus the number of men that Olivia has romantic options with is much higher than that of Angelica.  This is true by a factor of thousands of men.  It is even worse if you consider the number of men that Angelica could actually be attracted to or have feelings for in that small dating pool...

This is not a minor matter.  It is spelled out in Volume 1 Chapter 1 part 2, "

I believe that father got married because of what it meant to be married to Zola.

That alone makes her an important marriage partner. If a baron household doesn’t take an appropriate bride, then they’re declaring that they’re not a household of that rank. They’ll be made light of by other nobles, and some will attack them──it would start a war on the household.

In any case, they’d be unable to get along with other households as well as not being treated as barons.

It’s a case of ostracism."

Not marrying in the way that the society demands can be a matter of ostracism.  It can also be a matter of life or death, with a Nobility House War being meant to slaughter the family and take their properties.  This is something that can happen within the other families of the kingdom, no foreign invasion required.

The exception is Royal Exception.  If the Crown declares it ok, then the nobility must obey, or be stripped of their own rank.  This is why in the game the Queen's refusal to recognize Olivia's attempt to marry above her station could not be bypassed, until Olivia became the Saint.   

When Olivia becomes the Saint, she becomes a Pope like figure.  As the Pope was once called the King of Kings in Europe, the Saint is the Queen of Queens.  Once she outranked the Queen, the game would allow for marriage that the Queen never would have approved for a commoner.

in Volume 2 Chapter 2 part 1,

The reason being that I had beaten up Julian.

His mother wouldn’t forgive me for that.

Well Milaine was the queen──but in the game, she was a so-called enemy. As can be seen from her close relationship with Anjie, she was someone who would be hostile towards the protagonist, causing both her and Anjie to become the protagonist’s enemies.

As expected for a game marketed towards women. The mother-in-laws were loathsome.

She was someone who didn’t forgive the protagonist for having Julian fall in love with her. Saying this is obvious, but in the otome game, she was an opponent who tried to disrupt the relationship between the two.

It was a bit absurd. It was quite obvious to tell that she fit the template for a cruel person.

By the end, Milaine eventually recognized the protagonist.

That was caused by the protagonist gaining the position of a saint. The position of a saint had a very important religious meaning.

These explanations were just part of the overly-lackluster explanations in the game, though. There was no explanation for why a saint was so grand, but it was as if the protagonist was commended for doing a great service in the end.

The power of the protagonist herself was also pretty major, but to think that the power of saint was this immense.

The noble ranking system:

Rank 1: King and Queen

(Advanced Class at the Academy)
Upper Rank 2: Crown Prince or Crown Princess
Lower Rank 2: Prince or Princess/Duke or Duchess
Upper Rank 3: Royal Blood Nobles
Lower Rank 3: Minister - Types + Marquis/Marquess or Marchioness
(Lower/Upper) Rank 4: Count/Earl or Countess
(Lower/Upper) Rank 5: Viscount or Viscountess
(Lower/Upper) Rank 6: Baron or Baroness

(Regular Class at the Academy)
Rank 7: Baronet or Baronetess
Rank 8: Knight (Heritage)
Rank 9: Knight (Lifetime of Service)

(scholarship only at the Academy, with class type determined by ability)
Unranked: Commoners

https://en.wikipedia.org/wiki/Peerage_of_England

The Second major point for Leon to hate a promotion is taxes.   The light novel puts this on a price level.   

When paying to the adventuring guild, Chapter 7 Volume 1 states,

The Adventurer’s Guild is an official establishment from the country, so though they’re called a guild, they’re not really an independent organization.

It seems that they decided to call it a guild in the past. This lackluster setting is troubling.

“Of course. Thanks to that though, the country took away a portion of it.”

From twenty percent of the fortune I presented to them, the country took thirty percent of that.

However, the remaining treasure is all mine.

Rereading, this means 20% to the Adventuring guild rather than the family as I first thought (updating on 8/28/2023).  Due to the overwhelming likelihood of dying while adventuring, by national tradition, 80% of the treasure gained from a dungeon is tax and dues free, the base tax is applied to the guild dues, giving us the percentage for normal taxation.

Leon at the lowest level rank (7), pays the expected 30% to the crown.   This is the breakdown, which I think math wise it works out in 5% of total income steps.

Commoner: 15% taxes to the crown (15%). 

9th Rank: Knight (Lifetime of Service): 20% taxes to the crown.  

8th Rank: Knight (Heritage): 25% taxes to the crown. 

7th Rank: (Baronet/Baronetess): 30% taxes to the crown.  This is Leon's crown tax rate at the beginning of Episode 1. 

Lower Rank 6: Baron and Baroness - 35% taxes to the crown.

Upper Rank 6: Baron and Baroness - 40% taxes to the crown.

Lower Rank 5: Viscount or Viscountess - 45% taxes to the crown.

Upper Rank 5: Viscount or Viscountess - 50% taxes to the crown.

Lower Rank 4: Count/Earl or Countess - 55% taxes to the crown.

Upper Rank 4: Count/Earl or Countess - 60% taxes to the crown.

Lower Rank 3: Minister - Types + Marquis/Marquess or Marchioness - 65% taxes to the crown.

Upper Rank 3: Royal Blood Nobles - who do not pay taxes.

Lower Rank 2: Prince or Princess - who do not pay taxes /Duke or Duchess - 70% taxes to the crown.

Upper Rank 2: Crown Prince or Crown Princess - who do not pay taxes.

1st Rank - King and Queen - who do not pay taxes.

It is not hard to see how many families have been bankrupted by promotions, thus losing their status by not being able to pay the crown its taxes.  It also should be noted that the amounts are expected to be fixed.

So if your farm loses 50% of its profits from a drought, you are still expected to pay the same as if it was a regular crop or business year.  There is no mercy built into the tax system for bad years of income and some promotions are just seeking more money for the Crown.

Though it comes at the very beginning, there is something that is very important not to miss.  The most critical moment of Leon's life to come was buying the AI ship Luxion at the cash shop in his life prior.  Without this action, he never could have survived the world to come.

It's the only reason he was able to escape Zora's death trap for him.  It is the only reason he had any options at all.

Because he knew the ship's hidden item location, he was able to collect the item.  There was more quietly going on though...

While doing so he finds out that previous humanity was wiped out.   It is literally possible that he is on a rewritten Earth or Parallel Earth.

In this world, long ago, science created a group of humans with powers far beyond anything they could put up a fight against.  What came before may have been almost demigod-like beings.   Their power has greatly lessened in time.  

The reason I bring this up is that it is within the realm of possibility, that the entire world is a magical reworking of that world's reality.   It may be a genetically created demigod's wish made real.  The entire reality is trying to correct itself and play out in a logical fashion.   

It could be a general wish for what the world could be like that took an idea template that already existed.   It could be a wish for the world of an old book written on the game was something a female demigod wished for, or a classic game generations before her played.

from Volume 1 Chapter 2 part 3,

[Japanese...? You can read it? You people shouldn’t be able to use Japanese.]

Listening carefully, the sound was coming from the speaker in the room. It seems it wasn’t coming from the robot.

It appeared that the robot had an interest in me.

I cracked a joke while placing my hands on the control panel.

“My soul is of a genuine Japanese person. Justice for me is rice and miso soup every morning. Well, I’ve never eaten those here, though.──Perhaps you didn’t know what I just said, actually.”

This thing probably won’t understand even if I introduce myself as a reincarnated person. I think that if I say such a thing to other people, they’ll make a bitter smile while taking a distance from me.

[Soul? Is this the concept of transmigration?]

“So you do understand what I’m saying? Right, that’s what it is. Probably.”

I feel a bit glad having a conversation in Japanese after such a long time.

The control panel checked my genetic information from my palms, the registration for the master finishes, and then begins scanning as my whole body is wrapped in a red light.

As soon as the scan finished, the robot asked me another question.

[It’s confirmed from your genetic information that there is indeed traces of a Japanese individual. However, you are of the new humans. At the same time, you have inherited the genes of the the former humans. How perplexing. It is not feasible.]

“Is that so? Though, with this, the ship is mine now, right?”

[Indeed. From today, this spaceship is your property. Do you want to name it?]

The author of the series has left that much open for possibility.  It is a far greater depth of storytelling than I'm just in that game now...

There was a old Star Trek episode that explored this idea.  It was the episode, "Where No Man Has Gone Before."

If you are familiar with the episode, Kirk barely survives Gary Mitchell's awakening and the fate it could have brought humanity or the galaxy itself.  This Earth did not survive the awakening of the new human race.

from Volume 1 Chapter 2 part 2,

[Question. What year is it in terms of the solar calendar?]

“Agh! Solar calendar? As if I know! In terms of the Holfault Kingdom calendar...Gaaaah!!”

Electricity sprouted from the robot opponent’s hand, and my body turned numb from the agony as I yelled in pain.

Losing control, I acted violently to try and get away, but it wasn’t likely that I would escape anyhow.

[That answer is plenty. We had asked the same question many times...but we were defeated all the same.]

I was exhausted once the electric current ended, and the robot’s motion ceased. I was trembling and I couldn’t close my mouth, so I wiped my drool with the hand I was using to hold my sword.

“D, defeated? We? What are you talking──”

Were there even opponents that could make a cheat-level battleship lose?

[...This is about the new human race. The former civilization had been destroyed in the past before the advent of the new human race with overwhelming magic power.]

The magic users of today are far more tame.  At least, most of them are.   There is one know figure, known to appear once a generation, that may be as powerful or almost as powerful as the old gene spliced demigods themselves.

We can go deeper into the Saint later.   We haven't done enough set up to have that conversation yet.

That said, unlike her new human peers and instructors, Olivia has an innate understanding of what true magic is, from the very beginning.

from Volume 1 Chapter 6 part 1,

The True Protagonist

──I feel like hitting my recent-past self.

I showed off by telling Olivia that I could help teach her things, but I didn’t actually check her level of comprehension.

l mean, she didn’t say that she had trouble keeping up with the material around her!

And yet──

“I don’t understand it past this point. It has to do with magic, so apart from ordinary spells, magic utilizing art rites could also be applied, and──”

It was just us two holding a study group in the library.

In the beginning, I thought that it was going to be a study session with a girl in the midst of a bittersweet youth, but now I was breaking into a cold sweat while surprised at how vast Olivia’s knowledge reaches.

More precisely, Olivia’s intelligent.

“Y, yeah, wouldn’t it be like that?”

I’ve somehow managed to make it through using both knowledge I’ve studied up until now and from the game.

However, the intelligent Olivia nodded along to my vague words while seeming impressed.

“Right! The textbook isn’t right, there really is a mistake, isn’t there? I thought it was strange for some reason. I felt something off about the explanation on how using magic is supposed to feel. I’m glad I asked you, Leon.”

What to do...this child began pointing out mistakes in the textbook.

“N, not everything has an error. I think the textbook is important still.”

“I agree. About twenty percent of it feels off, but on the other hand, I agree with eighty percent of it.”

When I looked at Olivia’s textbook, it had signs of extensive use. Could it be that this girl has already finished reading through it? An amount worth one school term? It’s still June!

Yet she managed to do it even though some of the nobles have given up on the textbook after having a hard time on it?!

Luxion was to be the avenger of lost humanity.  The AI was ready to wipe out new humanity, in retaliation for the wholesale genocide of people like you and me.   

Unexpectedly, it found one last thread of that humanity in Leon's genetic code.  It found one last trace of the humanity it was programmed to protect and defend in Leon.

AND IT JUST GETS BETTER LMAO Trapped in a Dating Sim Episode 2

Domosenpai's review:

Japanese tea ceremony

https://en.wikipedia.org/wiki/Japanese_tea_ceremony

wiki quote

The Japanese tea ceremony (known as sadō/chadō (茶道, 'The Way of Tea') or chanoyu (茶の湯)) is a Japanese cultural activity involving the ceremonial preparation and presentation of matcha (抹茶), powdered green tea, the procedure of which is called temae (点前).^[1] While in Europe it is known as the "tea ceremony", it is seldom ceremonial in its practice. Most often tea is served to family, friends, and associates; religious and ceremonial connotations are overstated in European places. The English term "Teaism" was coined by Okakura Kakuzō to describe the unique worldview associated with Japanese tea ceremony, as opposed to focusing just on the ceremonial aspect, a perspective that many practitioners frown upon.^[2][3][4]

Zen Buddhism was a primary influence in the development of the culture of Japanese tea. Much less commonly, Japanese tea practice uses leaf tea, primarily sencha, a practice known as senchadō (煎茶道, 'the way of sencha').

Tea gatherings are classified as either an informal tea gathering (chakai (茶会, 'tea gathering')) or a formal tea gathering (chaji (茶事, 'tea event')). A chakai is a relatively simple course of hospitality that includes confections, thin tea, and perhaps a light meal. A chaji is a much more formal gathering, usually including a full-course kaiseki meal followed by confections, thick tea, and thin tea. A chaji may last up to four hours.

 

East Asian tea ceremony

https://en.wikipedia.org/wiki/East_Asian_tea_ceremony

An East Asian tea ceremony, or Chádào (Chinese: 茶道), Chadō (Japanese: 茶道) or Dado (Korean: 다도 (茶道)), is a ceremonially ritualized form of making tea (茶 cha) practiced in East Asia by the Chinese, Japanese, and Koreans.^[1] The tea ceremony (Chinese: 茶道 or 茶禮 or 茶艺), literally translated as either "way of tea",^[2] "etiquette for tea or tea rite",^[3] or "art of tea"^[4] in any of the three East Asian languages, is a cultural activity involving the ceremonial preparation and presentation of tea. The Japanese tea ceremony and Korean tea ceremony were influenced by the Chinese tea culture during ancient and medieval times, starting in the 9th century when tea was first introduced to Japan and Korea from China. One can also refer to the whole set of rituals, tools, gestures, etc. used in such ceremonies as tea culture. All of these tea ceremonies and rituals contain "an adoration of the beautiful among the sordid facts of everyday life", as well as refinement, an inner spiritual content, humility, restraint and simplicity "as all arts that partake the extraordinary, an artistic artificiality, abstractness, symbolism and formalism" to one degree or another.^[5]

At the very rudimentary level, East Asian tea ceremonies are a formalized way of making tea, in a process that has been refined to yield the best taste. Historical classics on the subject include the 8th-century Chinese monograph The Classic of Tea (茶经 Chájīng) and the 12th-century Chinese book Treatise on Tea (大观茶论 Dàguān Chálùn).