Suzukawa's lecture on how the Tokugawa dynasty maintained a stable government of Japan by securing their own interests and forgoing any ambitions to centralize power for themselves in favor of dividing power among their vassals foreshadows Kageaki's decision in the True End to run an independent mercenary colony and work only for those who insist upon requesting his aid even after learning the consequences. Kageaki has ceded the power and responsibility over Muramasa's actions to others instead of taking action on his own as he had been.
Konatsu likes to wake Yuhi up by getting him in a leglock, then pumps a fist in victory. That's some cruel foreshadowing, there.
After Suzukawa dismembers her, Konatsu should be spurting blood everywhere and dead within minutes...but remember that Shinkai's shinogi allows the user to control bodily fluids.
More than simply facing death with dignity, Shinkai implicitly causes the death of himself and Suzukawa. Once a great and acclaimed tsurugi, Shinkai has fallen into the hands of a lunatic serial killer, forced to commit monstrous crimes against the innocent yet unable to openly rebel against its master, no matter how unworthy. By withholding valuable information such as the basic instructions for combat and declining to give a verbal warning about the calorie meter, it guarantees itself an honorable death in battle at the hands of a worthy opponent.
Yuhi Nitta going into a violent rage after what Suzukawa did to his friends, even to the point of knocking a mushi off-balance, has grounds in something besides the awakening of his inner courage. He's actually an Otori and the other Otoris we see are both impressive in combat and have horrifying tempers. Guess he would've been a pretty good heir.
...Which leads into the fact that if he'd lived and taken over the Otori family, he might have been in a position to make very good on his plans to fight for righteousness and make the world a better place. The fact that he cannot, of course, is meant to underline to the reader that the decision to kill someone can have unanticipated consequences that run counter to the desires which motivated you to do so—one of the main themes of the game.
Is there any way that the brilliant and perceptive Yusa Doshin could have been unaware of Kuniuji and Sakurako's growing affinity for each other when he decided to perform his play? Unlikely. Having the two kill each other fits his sense of the theatrical all too well. He even specifically mentions the kind of flower Kuniuji sent her and that she was wearing in her hair so she'd think he might be in on it.
It's not impossible that in the case of the adoptive Parental Incest between Subaru and Kageaki that Subaru was a victim as well. It's mentioned that drugs were used to make young Kageaki "perform" against his will, so it may be that Subaru was in the same boat, manipulated by her husband and ancestor using some sort of powerful aphrodisiac or a drug like rohypnol which induced suggestibility. It would explain why she believed she could rebuild the old mother-son relationship she and Kageaki had had before, as well as her unwillingness to give him a parental role in Hikaru's life—she would rather just forget it all happened.
