Book 12 details the Genji's eradication of the last living members of the Heike. It features signs of karmic retribution to the form of an Earthquake, Yoritomo's renouncement of attempts to kill Yoshitsune, the execution Heike scions, and the return of the monk Mongaku, who attempts to save the last heir of the Heike family, Rokudai. We also see Yoritomo's rise in power, Yoshitsune's banishment and journey across Japan, and the death of Rokudai.
These chapters focus on how the Genji consolidate power, and how others respond to it. We see an earthquake which is said to be caused by the actions of the Genji, Mongaku giving Yoritomo the alleged skull of his father, and Yoshitsune becoming constable over Japan, to the disapproval of Cloistered Emperor Go-Shirakawa.
This section follows Yoritomo's failed assassination attempt against his brother Yoshitsune lead by the monk Tosabo, as well as Yoshitsune's banishment and journey across Japan.
These episodes describe the eradification of the last members of the Heike, including the exile of Tokitada, the murder of the Heike scions, and the execution of Rokudai.