Yoritomo sends men to the capital in order to stop the insurrection of Kiso no Yoshinaka. After defeating Yoshinaka, the Genji forces head westward to attempt to crush the Heike. The Genji forces attack the Heike by surprise at Ichi-no-tani, leading to the death of many men. The remaining Heike forces flea from Ichi-no-tani. Throughout the book, the theme of close male relationships is highlighted. One category is that of foster brother. High-ranking babies were suckled by wet nurses, and the age-mate child of that woman could become the foster brother to a lord. As foster brothers, the men would have been raised together, and the nursemaid's child would become one of the lord's most trusted vassals (the relationship was necessarily hierarchical). The other important male relationship we see is that between father and son. Both relationships help frame the pathos of the many deaths in this book.
Book nine begins with Yoritomo's men driving Yoshinaka out of the capital to put an end to his behavior. This results in the death of many of Yoshinaka's men, including Higuchi no Jiro Kanemitsu, and Yoshinaka himself.
Yoritomo's men enact a plan to march westward and attack the Heike, like Yoshinaka wanted to. The Heike are held up in their fortress at Ichi-no-Tani, and Yoshitsune comes up with a strategy to catch them by surprise.
The battle of Ichi no Tani finally begins. The Heike are crushed by the Minamoto forces, and many prominent members of the Heike, such as Etchu no Zenji Moritoshi, Taira no Tadanori, and Taira no Atsumori.
The Battle of Ichi-no-Tani draws to a close as the Heike warriors flee from the Minamoto, decisively defeated. To close the chapter, a tale is told of Kozaishou, Taira no Michimori's wife, and how she chooses to drown herself after losing her husband.