A manga by Fumi Yoshinaga, the author of Antique Bakery and a few other works, Ooku is the story of an alternate Japan. Our tale begins in the reign of Shogun Iemitsu, the third Tokugawa Shogun (1630s or thereabout).A plague, marked by fever and red boils, begins in a small mountain village.It spreads.Four out of every five plague victims die.All those who catch it are men (mostly young) and boys. Indeed, most young men and boys catch it.By the time of Shogun Ietsugu, some four generations later... things have changed.
The first arc (Chapters 1-4) takes place in the fourth month of the sixth year of Shotoku (1716) and focuses on two newcomers to Edo castle: Mizuno Yunoshin, a young man of a semi-impoverished Samurai family who decides that a lifetime sequestered as a courtier in the Inner Chambers of Edo Palace (with a healthy stipend sent home) is an improvement over the prospect of a 'good' marriage to someone other than the merchant's daughter he has known since childhood... and Tokugawa Yoshimune, a ruler of the rural Kii province who maneuvered herself into position to become Shogun upon the death of the sickly child Ietsugu and is taking a hard look at what is around her.
The second arc (Chapters 5-14) centers on the beginning of the whole mess as young Abbot Arikoto, third son of Duke Madenokoji Arizumi, is summoned to pay homage at Edo and finds out why no one has gotten a good look at Shogun Tokugawa Iemitsu for six years... the hard way.
The third arc (chapters 15-16): Iemitsu the Younger stands revealed, however even her official stance shows a hope of bearing a son and things returning to normal. Fat chance. She dies at age 27, leaving her eldest daughter Ietsuna (nee Chiyo) under the guardianship of Senior Chamberlain Arikoto (recorded in the official documents as O-man).
The fourth arc (chapters 17-24): The fifth Tokeguwa Shogun, Tsunayoshi, brings both the Ooku and Japan itself to the brink of revolt through her capricious rule while plots to gain power over and through her grow.
The fifth arc (chapters 25-26): A petty grifter named Sakyo is saved from a near lethal beating at the order of a passing noblewoman... who happens to be the next Shogun, Ienobu.
The sixth arc (chapters 27-29): With the child shogun Ietsugu sickly, the succession crisis heats up, threatening the lives of both senior chamberlain Ejima and actress Ikushima Shingoro.
The seventh arc (chapters 30-34): The story returns to Yoshimune as she begins her rule as shogun, institutes changes to better Japan and keep it isolated, commissions doctors to find a cure for the Redface Pox, and begins to bear children. With three daughters borne to her and a reputation as a popular ruler, Yoshimune's position looks very secure...but what of her successor? Will it be the elder but disabled daughter Ieshige or the younger but more hale daughter Munetake? Yoshimune chooses Ieshige, but the next shogun ends up known as a very ineffectual shogun.
The eight arc (chapters 35- ): Lady Okitsugu calls on the men of Deshima, the island where the Dutch are permitted to conduct trade with the Shogunate, to assist her in continuing Yoshimune's search for a cure to red-face pox...including a half-Dutch outcast named Gosaku.
Abdicate the Throne: Shogun Yoshimune steps down in favor of her eldest daughter Ieshige in vol. 8. Of course she failed to move out so....
Ieshige: note (after telling the officials seeking her advice to deal with ongoing famine and rioting as they see fit) "I-I-I know wha' the s-senior c-councillors will do. As always, they'll go s-stray to my muvva. S-so werefo' c-come to me at all?"
All Women Are Lustful: Somewhat deconstructed, as it is the prospect of children that so many women who cannot afford a husband are primarily paying for. Sakyo's story demonstrates, however, that most women still want the hottest sperm donor they can afford.
Alternate History: Diverges during the reign of the third Tokugawa shogun, Iemitsu, as the Red Face Pox dramatically alters the gender balance of Japan as a nation and then kills all the remaining male claimants to the shogunate.
Anatomically Impossible Sex: As an unfortunate consequence of growing up in a Buddhist monastery and then being cooped up in the Ooku as an adult, Keishoin has no idea how pregnancy works and hence keeps pressuring Tsunayoshi into promiscuity in hopes she will conceive a child...even when she's years past menopause. It also leads to the Edicts of the trope below, which are meant to lift her "curse" of infertility.
Animal Wrongs Group: Tsunayoshi's "Edicts on Compassion for Living Things" turn Japan's government into this, with punishment for swatting insects and execution for harming the packs of stray dogs wandering Edo.
Animation Anatomy Aging: Most noticeable with Tsunayoshi and Yoshiyasu since they're seen at various stages from girlhood to old age. On the male side, we see Gyokuei go from adolescent boy to senile grandfather.
Apocalyptic Log: The "Chronicle of a Dying Day" (and apparent source material for arcs 2-6) was commissioned as one by the Reverend Kasuga on her deathbed. It is not likely that she anticipated the man assigned to write it, the scribe Murase, being 97 when Shogun Yoshimune called on him for clarification on several traditions whose rationale has been forgotten.
Arranged Marriage: Part and parcel of the aristocratic life and a sign of a family's prosperity and status. As the effects of the Redface Pox grow worse, being able to marry at ALL becomes a sign of considerable prosperity. The shogun's formal consort is usually chosen from among the Imperial courtiers, in order to maintain Tokugawa influence in Kyoto, although of course she is also free to take concubines.
Art Shift: The art style occasionally shifts to highly stylized figures that resemble old-fashioned Japanese woodcuts, usually for generic scenes of everyday life that do not involve actual characters.
Awesome Moment of Crowning: The end of Volume 3. Strictly speaking it was only the annual ceremony of tribute and fealty to the long-reigning Shogun Iemitsu, not an actual coronation, but the moment the screen behind which said Shogun (supposedly) sat was raised for the first time in the better part of a decade and a young woman commanded all to look upon her as their new ruler? Still counts.
Bears Are Bad News: The manga starts with a little boy being mauled by a bear. This may or may not be related to the fact that his brother is the first victim of the Red-Face Pox.
Bishōnen: By the bucket—at least in the Ooku itself. The rest of the country is a bit short on them.
Bi the Way: The line between this and Situational Sexuality is blurry, because Edo-era Japan had a fluid concept of sexual orientation and the gender ratios are so skewed, but Yoshiyasu and Manabe both seem to have had romantic and possibly sexual relationships with both genders.
Broken Bird: Iemitsu as a teenager, so much. While she matures into a formidable woman, Iemitsu is still deeply traumatized by everything she's been forced to endure.
Cast Full of Pretty Boys: The Inner Chambers are this by design. The men serving in Edo Castle are divided into two groups based on whether they are considered pretty and accomplished enough to appear before the shogun. Those who are not are restricted to menial or administrative work.
Chekhov's Gun: Gyokuei murders the cat Murasaki and frames it on Shigesato as revenge for the attacks on himself and Arikoto. He later believes this to be the cause of Tsunayoshi's infertility; the gods punishing the sins of the father through his daughter. This leads to the Edicts on Compassion for Living Things.
Ietsuna became shogun at age ten, although she did not reign in her own name until she was twenty-two.
Yoshimune herself, after the deaths of her mother and two sisters, found herself in charge of Kii province at the age of twelve.
Ietsugu, the seventh Shogun, died at seven, after a reign of three years.
Clueless Chick Magnet: Poor, poor Arikoto. Women of all stations making calf-eyes at him when he was a monk was one thing, but the teenaged girl he pledged his late beloved he would raise as a daughter making an Anguished Declaration of Love? Awkward.
Costume Porn: Lampshaded a bit in the story itself, as the idleness of the Ooku makes this one of the few amusements available to its residents...but Mizuno attracts Yoshimune's attention by going with something more subtle.
Deadly Decadent Court: There is a lot of jockeying for power and backstabbing throughout the series, but two eras stand out from the rest.
In the second half of Tsunayoshi's rule, her court's luxurious excess is becoming a drag on the economy and the shogun is no longer really in control of her councillors' actions. Emmonosuke's rivalry with Keisho-in to find a concubine to conceive another heir is getting out of hand. Tsunayoshi's delay in naming an heir also leads to several successful and attempted assassinations, as Tsunatoyo's retainers attempt to ensure that the cadet Kii branch is not a viable alternative.
Once Ienobu's succession is secure, things calm down as she's still of childbearing age and soon produces an heir. However, Ienobu's untimely death and the obvious frailty of the child shogun Ietsugu lead to a breakdown of discipline in the Inner Chambers and a resurgence in assassinations as Yoshimune moves to ensure that the other cadet branches will not impede her succession.
Deathbed Confession: Not technically a deathbed one, since she lived a month or two after it, but considering it was her last conversation with Yoshimune, the spirit of the trope is still there. Hisamichi confessed in their last conversation that she poisoned Yoshimune's sisters and the closest rival to the throne to ensure Yoshimune became shogun. It's not entirely clear how Yoshimune took the news, but the parting certainly seemed amicable enough.
Death by Childbirth: Not explicitly stated, but it is strongly implied that the numerous miscarriages Iemitsu suffered in her efforts to bear a male heir were a major contributor to her early death. Her granddaughter Ienobu also suffers multiple difficult pregnancies that eventually shatter her already fragile health.
Death by Sex: It is a rule dating from the time of Iemitsu for the first courtier of the Inner Chambers to lie with an unmarried Shogun to be discreetly executed for causing injury to her person (Iemitsu the Younger had a truly horrific First Time and could not understand that it isn't always like that). Too bad nobody told Mizuno or Yoshimune ahead of time.
Disposable Sex Worker: The ladies Kasuga hires for the monks are murdered, even after Aritoko breaks his vows. It's implied Kasuga was going to have them killed no matter what, in order to prevent them from ever speaking of what was going on in Edo Castle.
For Yoshimune, it's good to be the Shogun. Within the Ooku, she's known for just grabbing a guy out of the blue for a quickie in the bushes or a supply closet.
Tsunayoshi pretty much destroyed the family of her privy councillor Narisada (a woman she claimed to be very fond of) this way. She had had an affair with Narisada's husband before becoming shogun, and after her ascension made him her unofficial concubine since she found the men of the Ooku boring. Then, when his health started to decline, she forced his (nearly identical) son into the Ooku to serve as her Sex Slave, despite the fact that HE was also already happily married.
Drinking Contest: Sakyo is first seen winning money in one. It seems he regularly drinks women under the table on a bet. Even though he's well known as a scam artist by now, women keep taking the bet because he's absolutely gorgeous and the prize is a night with him.
El Cid Ploy: The original plan was to conceal the death of Shogun Iemitsu until someone could sire a male heir on his bastard daughter and continue the Tokugawa line. Kasuga's son was the body-double at the fealty ceremony, while Chie was dressed as a boy to pass for Iemitsu's catamite, so she could enter and leave the shogun's chambers without arousing suspicion.
Evil Chancellor: Emonnosuke, despite the overt Manipulative Bastard streak, ultimately averts this trope. His clever management is the only check on the vast expense of maintaining the Inner Chambers during Tsunayoshi's rule and his loyalty is squarely with the shogun as is his love.
Evil Matriarch: Blessed Kasuga. Full Stop. Yes, she was 'merely' Iemitsu's wet nurse. She still counts.
Faking the Dead: Mizuno Yunoshin, in order to get around the Secret Swain law.
Fatal Flaw: Pride, for Yoshimune. While her judgement was, in most respects, compassionate and very practical, she could not get around her traditional samurai class-bias against merchants and the developing cash economy. It never occurred to her that cash taxes on merchants could replace the rice stipend system that was placing ever-harsher burdens on farmers.
Foregone Conclusion: The second story arc. From Yoshimune and Yunoshin's story, we know that Kasuga's and Iemitsu's attempts to restore male-line succession are doomed to failure, since the shoguns will still be female four generations later.
The 47 Ronin: As part of the In Spite of a Nail, this incident still occurs, but in this context, it is instead mourned primarily as a waste of good men. In an interesting twist, the Ooku!verse Kira is female, but Ooku!Asano is from one of the very last families to have held on to male succession. Hence the unusual concentration of men among his retainers. By this time, Tsunayoshi is elderly and her old-fashioned shock at Would Hit A Woman leads to a wildly unpopular decision not to punish Kira.
Gendercide: Comparatively mild with the gender ratio stablizing at 1:4, but it still has dramatic ramifications.
Gender Rarity Value: The men are Type 2. There are so few healthy, fertile men (as even some who survive the Red-Faced Pox are permanently disabled by it) that they are banned from any kind of risky or stressful activity—and that includes governing. A surviving son is seen as a valuable source of income, either from stud fees paid by peasant women or a dowry from a woman rich enough to buy a husband all to herself, but will likely never engage in any other productive activity. We see a peasant woman abandoning her elderly father on a mountainside, because he has outlived his only purpose.
God Save Us from the Queen!: Tsunayoshi borders on this. While she certainly meant well at times, the unpopular Edicts, her decision on the 47 Ronin, ineffective councillors who isolate her from actual governance, a tanking of the economy, and finally her sheer longevity and delay in naming her heir ultimately push her into this trope, at least in the eyes of the populace. And the truly tragic thing is she's aware of this, and would welcome a kingslayer to end her life. It's not entirely clear if Yoshiyasu murdering her was a Mercy Kill or a Woman Scorned.
Glorified Sperm Donor: Yoshimune views the members of the Ooku as this, with a rotation schedule for her visits to her multiple regular partners and frequent quickies with servants. Yoshimune's deliberate lack of favoritism prevents harem power grabs, since none of her concubines have special access to her to use as leverage. When she finds herself pregnant, it also means that none of them can gainsay her when she names a weak and malleable one-night-stand as the father.
Gonk: Ejima is exceptionally hairy and coarse-featured by any standard, and when presented to sheltered aristocratic girls who are more familiar with Bifauxnen stage actors than actual men they tended to react with horror.
Guy on Guy Is Hot: Tsunayoshi orders this at one point during her period of depraved promiscuity after Matsu's death. For once, not played for laughs.
Heir Club for Men: Kasuga is a die-hard proponent of the Club because of her devotion to Iemitsu the Elder, but most of Japan has already given up on male-line succession by the time Iemitsu the Younger reveals herself. By the fourth post-Pox generation, almost no one even realizes any more that things were ever different, and the idea of male heirs to noble houses is scandalous.
Hidden Backup Prince: Chie/Iemitsu ends up serving this purpose. As an illegitimate daughter by a commoner, only Kasuga even knew she existed until the Red-Face Pox killed all male claimants to the shogunate...at which point she was forcibly taken from her mother to serve as the progenitor of a new line of shoguns. Despite originally being a pawn in succession politics, Iemitsu ends up ruling in her own name as a grown woman.
The closing of Japan had a rather different rationale here. While the Dutch factory at Deshima remained open, every trip the local Kapitan made to pay homage was precisely stage managed to conceal the altered gender balance and the gender of the shogun. The fear was that other countries would try to invade at a time when Japan could not field an able-bodied army to repel them.
Edo Castle served as a miniature version for several years after the death of Shogun Iemitsu the Elder.
Hope Spot: Just as all of Nagasaki braced itself for another round of Redface Pox... all of the infected were suddenly cured with no explanation.
Ill Girl: Ietsugu unfortunately inherited her mother Ienobu's weak constitution, making her reign brief and unstable.
Implausible Hair Color: Justified in Gosaku's case. He's the blond son of a Dutch trader and a Dejima prostitute, and so favors his father in appearance that Gennai mistook him for a full-blooded Hollander.
Impoverished Patrician: Yunoshin and Sugishita in the first arc, various aristocrats from Kyoto later on, including Arikoto and Emonnosuke. Truth in Television as the Imperial court was much poorer than the shogunate at this point in time and the wealth of the samurai class declined sharply during the Edo period.
Incest Is Relative: Crops up a couple times in this series (not entirely surprising when there are so few men available to begin with):
Brother-Sister Incest: Akimoto and his sister Kinu slept together, resulting in a daughter. Emonnosuke was quite amused when he found out, and notes that even the origin of Japan was based on this trope. At least it appears to have been quite consensual, because Akimoto and Kinu clearly adore each other and did not wish to be separated...
Parental Incest: ...which is more than can be said about what happened between Sakyo and his mother. She started raping him when he was 14 and continued doing so long enough to have two children by him. Little wonder he was willing to work at Ienobu's household with no pay if it meant getting away from her.
In Spite of a Nail: Despite being the opposite sex, the Shoguns of this timeline share the same names and reign dates and have very similar personalities to their historical counterparts. Due to the closing of Japan to foreigners, its relationships with the outside world remain much the same as well.
Jidai Geki: The Reverend Kasuga lived through the tail of the Sengoku period and the main body of the series is set in the early Edo period. Although the swordfights this genre is known for are notably absent, with the ronin population so drastically decreased.
Knight Templar: The Reverend Kasuga. She murders and kidnaps without batting an eye, and will use the only person she is halfway fond of as a brood mare. Her motivation?
"A country at peace. Without war."
There's some genuine feeling involved in her quest for peace at all costs: her birth clan and marriage were utterly destroyed in the civil war over the shogunate.
Lady Land: Not only have women supplanted men in all remotely dangerous or strenuous occupations, but by the time of Yoshimune they have also almost entirely sidelined men in rulership and administrative positions.
Married to the Job: Yoshimune certainly enjoys sex frequently and vigorously but she's far too preoccupied with governance to develop strong attachments to her partners or her councillors (except for Hisamichi, who she became friends with before her unexpected succession to lordship). Even when taking a relaxing bath, hunting in the royal park, or in the middle of delivering her first child, Yoshimune's also thinking about affairs of state. Her relative lack of social graces does not much help. In volume 8, it becomes obvious that this has caused issues in her relationships with her daughters.
A Match Made in Stockholm: Subverted when Arikoto learns that the Shogun in whose name who he was effectively kidnapped and forced to abandon his vocation is as much a prisoner as he is. And possibly even more of a victim. The affection that develops between them is more solidarity in shared misfortune than a captive falling for his captor.
Matriarchy: Of the Patriarchy Flip variety. There was a moment relatively early in the Red Face Pox era when massive polygyny could have been adopted as an alternate solution to the gender imbalance but the importance of family identity in Japanese culture and the shogunate's fear of consolidation of noble houses lead to female-line inheritance instead. Within four generations, it's considered a bit scandalous to suggest that men should EVER be allowed to inherit. When Shogun Yoshimune is throwing out pretty much everything she was brought up to believe about gender roles, she still points out that matrilineal descent has the practical advantage of being much, MUCH easier to prove.
Modest Royalty: Shogun Yoshimune. When one uses the gift of ornate robes as an excuse to dismiss a privy councillor, is known to meet with high officials in what amounts to her pyjamas, and continues to issue edicts while in labor it is hard to describe a ruler as anything else.
My Beloved Smother: Kasuga to Iemitsu the Elder. Despite only being his wet nurse, she's far closer to him than his biological mother. Iemitsu complains about Kasuga constantly nagging him to stop sleeping with boys and produce an heir.
Terutsuna, a woman who had been raised as a man, jokes that the only time she remembers she's a woman is when she gets her period.
A tearful Tsunayoshi confesses to Yoshiyasu that she entered menopause long ago and cannot conceive another heir.
Yoshimune started to figure out she was pregnant when she realized she hadn't had her period that month.
Oh Crap: When Shogun Yoshimune informs her childhood friend and longtime retainer Hisamichi of her intent to replace all the privy councillors with a single intermediary to serve as a go-between between her and both the councillors and "that troublesome lot in the Inner Chambers," the latter could only giggle at first.
Hisamichi: "Dear me! That sounds like a most difficult post indeed!"
Yoshimune: "If so, then thou hast little reason to laugh, Hisamichi. 'Tis thou who shall fill the post."
Only Six Faces: Genderflipped from the usual pattern, as this is most noticeable with young male characters. It's actually thematically appropriate since the inhabitants of the Ooku are regarded as pretty much disposable and interchangeable.
Persecution Flip: Inversion of traditional gender roles is a major part of the premise, after all.
The most interesting flip is in attitudes towards strength and endurance: while men are still acknowledged to be capable of greater brute strength than women, they are perceived as too fragile and lacking in endurance to be useful for heavy physical labor.
This actually intensifies another aspect of the persecution flip: because men are seen as so fragile, they usually don't take over traditional female tasks like cooking, textile work, and childrearing—women just do everything except provide sperm. That means a man whose fertility is compromised by illness or age is treated as even more expendable than an infertile woman in the same historical period, who might still be seen as useful around the house.
Ejima develops a major Fat Girl complex about his hirsutism and extremely burly body, because standards of attractiveness have shifted so far towards the feminine, especially in the upper classes.
All Zenjiro wants out of life is to be able to work as a chef, but high cuisine is seen as so wholly a female preserve that he has to enter the Inner Chambers to rise above the level of sous-chef, despite his obvious skill.
Pity Sex: Yunoshin has a reputation for a variant of this. While he is hopelessly in love with O-nobu and would sooner clean sewers than sell his services (despite being healthy, good looking, and possessed of noble enough bloodlines to command a decent 'stud fee'), he often tries to get unattractive, dirt poor women with child just for the asking. By making sex a favor instead of a business transaction, Yunoshin is able to name his terms, and avoids the kind of partner abuse Sugishita suffered.
When Kasuga presents several prostitutes to Arikoto and his travelling companions and tells them to "enjoy the company" of them at a guest house, the lot of them proceed to have a night of dancing and silly party games instead of sex. Then Kasuga and her goons step out from concealment to spell things out.
In a very real sense, many of those who sell themselves into the Ooku are shooting for this. A life among the ranks of those 'Unworthy Of Our Liege's Sight' means that one will never even be asked to have sex with a woman again (at least until Yoshimune shows up).
Poisonous Friend: Baron Hisamichi not only had the top rival from another Tokugawa cadet house poisoned, but personally murdered both of Yoshimune's sisters to smooth the way to her best friend's eventual succession to the Shogunate. She was around twelve when Yoshimune became Lord of Kii.
Poor Communication Kills: Blessed Kasuga was not going to let Abbot Arikoto leave Edo alive anyway, so why not level with him about needing his services as a stud and appeal to his patriotism and/or love of peace instead of starting off with the dark hints and murders? She may have wanted him to fear her from the beginning but it was still a crappy strategy given that she could still start cutting bits off his friends later.
Praetorian Guard: A secondary purpose for gathering so many male samurai in one place, especially early in the Ooku's history, when the rule of law was not yet well-established. Even in the series' present day, the men of the harem are required to train in martial arts and to patrol the castle.
Primal Scene: Tsunayoshi catches Yoshiyasu and Keishou-in, her best friend and her father in the act and has a breakdown.
Put on a Bus: Only natural this happens, given this story takes place over many decades...
The Bus Came Back: ...but on occasion, this happens too. Gyokuei spent an entire arc away, only to return as the father of the next shogun. Arikoto reappears twice in his old age, once to visit Gyokuei one last time, then later to pay his respects to the now deceased Gyokuei. And Yunoshin has a cameo where he expresses his desire to join the local fire brigade.
Rags to Royalty: The (reported) fathers of the Shogun's children rank only slightly below the official consorts normally imported from the Imperial court in Kyoto, while the father of the Shogun herself ranks at least as high as the latter. This means that men who start out as common laborers, gigolos, scam artists, and beggars have found themselves the peers of the Japanese Emperor's kinsmen.
Reasonable Authority Figure: Shogun Yoshimune. While Yoshimune can be severe when she feels the greater good requires it, she also tries to get rid of pointlessly harsh laws that have remained on the books for decades just because of the weight of tradition. She's probably as strong a ruler as Iemitsu but without the ruthless streak: both drastically reduce the population of the Inner Chambers in order to save money and stop hoarding eligible young men...but while Iemitsu has the men she dismisses imprisoned in Yoshiwara to serve as prostitutes, Yoshimune sends them back to their families to seek honorable marriages.
Red Light District: Yoshiwara in Edo, which fell on hard times with the coming of the Red-Face Pox and was later revived by Iemitsu to provide the women of the city a chance at motherhood.
Royal Harem: The main setting of the story. The Ooku is gender-flipped from the male ruler/female concubines pattern but otherwise has all the classic features: strictly segregated from the outside world, full of scandalous sexual behavior and luxurious excess, and constantly involved in political machinations. The different ways in which men end up in the Ooku are explored several times: some are coerced like Arikoto and Sadayasu and become SexSlaves; some like Sutezo choose to enter the harem simply because it's a drastic increase in their standard of living; others like Emmonosuke and Kashiwagi are ambitious and want to gain access to the shogun; some are escaping much more brutal forms of prostitution like Sugishita; Akimoto and Yunoshin both entered after falling in love and then finding the prospect of an arranged marriage unendurable.
Scarpia Ultimatum: Blessed Kasuga chooses an indirect method. Rather than threaten Arikoto directly she has one of her men start killing his companions and the courtesans she sent in to tempt him into violating his priestly vows right before his eyes.
Screw the Rules, I Make Them!: Averted. As horrified as she was by the whole "Secret Swain" bit, and despite her intent to rescind the edict once she found out about it, Yoshimune had to let the execution of Mizuno go through... one way or the other.
She Is the King: Women with leadership or administrative roles, as well heads of noble or samurai households, do not just take on what used to be exclusively male titles: they also use alternate masculine names for records and official functions. When men are mentioned in records or official functions (generally only as "spouse of" or "concubine of" an important woman), they use alternate feminine names. By the time of Shogun Yoshimune few even think twice as to why. Ironically, the original reason for giving female leaders male-sounding names (begun with female heirs impersonating their dead brothers, and made official with Iemitsu the Younger choosing to retain her father's name) was so that the era of female rule could be concealed and forgotten once the gender ratios went back to normal, since there would be an unbroken continuity of male names in the historical records. (The practice of giving men female-sounding "married names" began with Iemitsu the Younger mockingly re-naming her male concubines as if they were women.) Instead, that continuity leads to later generations of female leaders forgetting that men were ever the dominant gender.
Shrouded in Myth: By the time Yoshimune becomes shogun, only the very, very oldest inhabitants of Japan can remember a time before female rulers, and 50/50 gender ratios are beyond living memory. An educated few are aware that the current situation has only existed for four generations and that the rest of the world is unaffected. For most, the time since the change has grown in the retelling from "a few hundred years" to "a thousand years" to "in the time of the gods".
Male homosexuality is considered quite normal in the Ooku, much to the shock of newcomers such as Yunoshin. Many men in the Ooku will spend few or no nights with the shogun but never see any women besides her, so the other occupants are their only available sexual partners.
Outside the Ooku, many merchant- and peasant-class women lust after male-impersonator kabuki actors, since sex with men is a luxury often too expensive to indulge in except to produce a child. It would be shocking in this context for men to sleep with each other, since it wastes sperm that's worth its weight in gold.
Noblewomen are implied to have romantic and sexual relationships with one another, since their consorts are chosen for family connections and fertility, not for companionship. Yoshiyasu clearly desired to have this kind of relationship with Tsunayoshi, and Manabe and Ienobu may or may not have been in a sexual relationship.
Sketchy Successor: Shogun Yoshimune would have been a tough act to follow for anyone, and her daughter Ieshige's insecurities (far moreso than her speech impediment or vaguely defined physical disabilities) render her almost wholly ineffective.
Slice of Life: There are numerous interludes in the various flashback arcs showing how common farmers and townspeople are adjusting to the death of menfolk.
Star-Crossed Lovers: Nothing seems to go right for Arikoto and Iemitsu. The next couple Shoguns have problems of their own along these lines.
One-sided in Ietsuna's case, as the only man she ever desires is Arikoto, who loves her as a daughter.
Tsunayoshi and Emmonosuke were infatuated with each other for many years, then spent a single night together before Emmonosuke's untimely death.
Usually shoguns are virtual strangers to their official consorts, never meeting before their wedding day and rarely spending any time together after. Ienobu had what could have been a happy marriage to her official consort...and yet she was forced to set him aside and take healthier concubines in order to produce an heir.
Ieshige and her official consort, Prince Naminomiya, were also very fond of each other, bonding over being considered physically unattractive. Unfortunately, Naminomiya died shortly after Ieshige miscarried their first child, and she was unable to believe any other man could truly love her.
Succession Crisis: This is a series about harem politics, so it's rare that there ISN'T some sort of infighting going on about succession to the shogunate.
The death of Shogun Tsunayoshi's child and the politics surrounding who to name as her heir add to the (considerable) troubles of the latter half of her reign.
The story kicks off with one, because of the death of the child shogun Ietsugu. Her regents have recently been brought down by a scandal so not only is there not an heir apparent there is no named successor, either. That means the heads of all three cadet branches of the Tokugawa have a shot at the shogunate. Yoshimune of Kii wins because she has been quietly preparing for this day for years and Hisamichi has been preparing for even longer and is ready to move immediately.
Yoshimune gives birth to 3 surviving daughters but still can't avoid a succession crisis, as the oldest, Ieshige, has significant physical and emotional disabilities. Her councillors push for naming the second daughter, Munetake, as heir despite the Tokugawa policy of strict primogeniture. Yoshimune decides that Ieshige is still actually of sound enough mind to take the throne and refuses to remove her from the succession.
Sweet Polly Oliver: In the first years after the coming of the Redface Pox, several noble houses dressed a daughter in drag and discreetly substituted them for a dead heir. Iemitsu stopped that practice cold just by showing up, although those taking 'masculine' positions still take male names.
The Wrongful Heir to the Throne: By the end of her reign Tsunayoshi believes herself to be this, and appoints her half-sister Tsunashige's daughter as her heir.
Time Skip: Several in Volume 4. After Arikoto becomes Senior Chamberlain, the story skips to Iemitsu's death, then skims over most of Ietsuna's childhood, then goes from Arikoto resigning as Senior Chamberlain straight to Tsunayoshi's succession.
Tomboy and Girly Girl: The two Shoguns Tsunayoshi and Yoshimune. Taught since childhood that she should strive to be attractive to handsome men, Tsunayoshi was shocked at Yoshimune's alternative view that since she has no interest in bishonen, it stands to reason that there would be men interested in plainer girls like her.
Yoshimune. Not only was she from a minor branch of the Tokugawa family, she was the third daughter of it, so it was unlikely that she'd even become head of her own family, much less Shogun. A combination of the deaths of her older sisters and the sickly nature of the branch that Ienobu came from saw her take the shogunate.
In the only meeting they had together, Tsunayoshi notes to Yoshimune that she herself was an Unexpected Successor, being the third daughter of Iemitsu, and having inherited the throne when her older half-sister Ietsuna died without issue. The historical record shows that the real Tsunayoshi was picked over his other older brother Tsunashige, Ienobu's father. In the Ooku-verse, it is implied (see vol. 3) that, among her concubines, Iemitsu definitely preferred Gyokuei (Tsunayoshi's father) over Sakyo (Tsunashige's father), as Gyokuei was Arikoto's surrogate and she saw a bit of herself in his insolence, while Kasuga had matched her with Sakyo merely because of his family background. Since the shogun's father wields considerable influence, it's not surprising she'd favour the concubine she trusted more.
Unlucky Childhood Friend: O-nobu, the daughter of a wealthy merchant house and longtime neighbor of Yunoshin. The guy she marries shortly after his sudden death from illness within the Ooku was reported? Well, maybe they do look a bit similar....
On the Spear side: While a few men like Sutezo do revel in the money available by selling themselves and enjoy having their pick of women to sleep with, many more are hired out or married off against their will and the living and working conditions for prostitutes can be horrifying. Sugishita worked as a prostitute for years and was abused by many of his customers, then after marrying he was beaten and starved by his inlaws for infertility. He was so terrified of having to return to that life that he chose to enter the Ooku instead. Yunoshin mentions that he worked any menial job he could find, up to and including cleaning sewers, to avoid having to trade sex for money. Even Emmonosuke, a noted scholar with an impeccable aristocratic lineage, was little more than a very classy rent boy until he entered the Ooku.
On the Distaff side: There are far fewer female characters involved in actual prostitution (because demand has largely collapsed) but they also avert Unproblematic Prostitution. The sex workers Kasuga hires to tempt Arikoto include a woman sold into sexual slavery by her lout of a husband, Ikushima Shingoro finds most of her clients tedious at best and nauseating at worst, and the women who service foreign sailors in Dejima are ostracized along with their half-European children. Taking "prostitution" in a broader sense, Iemitsu and Tsunayoshi both profess to feeling like whores when affairs of state force them into bedding men they barely know in hopes of producing an heir.