Reiri assumes Nobukatsu's identity but Oyamada betrays Katsuyori and denies him entry. Reiri is needed to hold off the pursuers so the other body double takes over and is the one who committs seppuku as Nobukatsu; maybe Souzou dies or maybe he doesn't. Historically the Incident at Honnoji (June of 1582) happens not too long after the destruction of the Takeda at Tenmokuzan and when Ieyasu is fleeing back to Mikawa, Anayama gets separated and is murdered by unknown killers. The legend is that it was vengeful Takeda retainers but I assume for the sake of the story it'll be Reiri who tracks him down and kills him. I'd assume she then settles into a peaceful, if melancholic, life afterwards.
