These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Akinari Kato is a tyrannical Daimyo who rules the lands of Aizu in a hedonistic hell where he has girls abducted to serve as slaves and toys for his pleasure before allowing his pet psycho squad, The Seven Spears, to torture them to death. When his vassal, Mondo Hori, rebels to save his daughter from such a fate, Akinari has him and the Hori men tortured to death. Throughout the series, Akinari abuses, tortures and rapes those who fall into his clutches, and when he is so terrified by Jubei Yagyu's constantly hounding him, he makes himself feel better by abducting and violating the innocent daughter of a lord who had the bad fortune to host him for a night. When he finally gets a hold of the surviving Hori women, Akinari sentences them to death by crucifixion and orders it to be made as drawn out as humanly possible.
Uroshido Koshichiro is the leader of the Seven Spears and Akinari's right-hand-man. A talented Master Swordsman who serves as an Evil Counterpart to Jubei with equal skill, but none of the honor, virtue or goodness, Koshichiro opens the series dragging the men of Hori before the Hori women and then promptly initiating a slaughter of the women just to hurt the men more. Koshichiro leads the Spears in their disposal of women Akinari is bored with and kidnaps newlywed couples to frame Jubei's ally Princess Sen as a rapist, forcing concubines to rape the men and giving the women to Akinari. While Koshichiro is seen as a Worthy Opponent by Jubei, Jubei makes it clear it is only because he deeply desires to face Koshichiro's skill against his own and makes it clear that he has nothing but hatred and contempt for the man himself.
Jubei and Takuan are trying to discuss their options for escape from Akinari's castle. The entire time, Oyura, under the influence of a powerful aphrodisiac, keeps crawling all over Jubei and begging him to have sex with her, while he just frowns in exasperation and tries to fend her off. Takuan seems more amused by Jubei's plight than anything else.
The Spears cross it when they break into the divorce temple to butcher the Hori women in front of the Hori men
Akinari is a nasty bastard from the get go, but his rape of Otone is what seals the deal
Dohaku's is either ordering innocent women killed as a message to Jubei, or his reaction to Oyura's death at his own hand.
What Do You Mean, It's Not Symbolic?: Koshichiro tends to place a cherry blossom twig between his teeth before he starts killing. It's a symbol for death and life's fragility. The series never tells you this, though.