Finish watching the penultimate episode and wow...that ending, I am a bit speechless, it really hits you in the gut with raw emotions. Having read the book, I knew it was coming, but I was impressed they did it better than I imagined.
Mariko decides to take her fate in her hands. You can see she displays a confidence and self-assurance that wasn't apparent in the earlier episodes. She knew her mission and executed it to perfection, you can glimpse a hint of satisfaction on her face as she outplays Ishido. Through her, the fate of Japan will be decided, to some extent. Anna Sawai does a stand up job portraying her in this episode.
Ochiba by contrast reveals she still care for Mariko and her flashes of concern shows both her lingering sisterly affection for Mariko and also the realization that Toranaga, through Mariko, is outmaneuvering the council of regents.
Blackthorne too also comes to understand what "Crimson Sky" truly means, as embodied by Mariko. From his initial disgust and horror at samurai rituals, he comes to accept it and honor Mariko's desires.
Yabu also has a key role in the episode. Throughout the series, we see him as sadistic and despicable, yet also a comically incompetent version of the scheming "Littlefinger" from Game of Thrones. In this episode though, he has to finally choose which side he will ultimately be loyal to. Tadanobu Asano should be praised for effectively portraying Yabu to draw out the audience's conflicting emotions on him. You hate his character Yabu for what he does yet at the same time you can't help but be invested in that character and focus on him.