From a reviewer:
This is a chronicle of Yoshitsune, brother of Minamoto Yoritomo who was ruler of the first military government in Japan from 1192. In the decisive battles with the Taira clan in the Gempei War, Yoshitsune had shown himself to be a superb soldier, master swordsman, and none-too-shabby with the bow either. He was also a brilliant general and a master military tactician, and achieved near-legendary status due to his efforts.
Problem being, Yoritomo is a somewhat paranoid chap, and he starts to believe that his little brother will soon fancy being Shogun himself. His mind is also poisoned by scheming advisors who have their own reasons for wanting our hero out of the way, and eventually Yoritomo decides the only option is to have his innocent brother's head on a stick. Yoshitsune gets wind of this though, and scarpers with his loyal band of retainers. Pursued by Yoritomo's men, he undergoes all sorts of challenges to his life, sanity and the loyalty of his group, and frequently has to engage his enemy when vastly outnumbered.
Based on real events, this is my favorite example of Japanese Chronicle history. All the characters are real and the general thread of the story is accurate, but there's absolutely no historical basis upon which to base the events. But historical accuracy wasn't the author's aim. Writing in the 17th century, the author was alarmed and rather disgusted with the general demeanor of the samurai.
Traditional values such as honor, loyalty, austerity and practice of the arts had been eroded and replaced by self interest, material desires and downright laziness. This chronicle highlighted the virtues of the true samurai warrior, represented by Yoshitsune, and the willingness of his retainers to lay down their lives for their lord. It was designed to be a wake-up call and shame the author's contemporaries into a return to 'the good old days.'