Blood revenge – or katakiuchi – represents one of many defining principles that characterize the Japanese samurai warrior; this one act of honorable violence served as an arena in which warriors could demonstrate those values which have come to embody the word samurai : loyalty, honor, and personal sacrifice. Blood revenge had a long and illustrious history in Japan – first, as the prerogative of the gods in the Kojiki, then as a theoretical debate amongst imperial royalty in the Nihongi, and at last entering into the realm of practice amongst members of the warrior class during Japan’s medieval period. Originally, blood revenge served a judicial function in maintaining order in warrior society, yet was paradoxically illegal in premodern Japan. Throughout the medieval period, the frequency of blood-revenge undertakings likely increased, acquiring social legitimacy despite the practice’s illegal standing; however, under the rule of the Tokugawa bakufu, blood revenge was granted the legitimacy of law as well through the legalization of this practice. The social and cultural influences of blood revenge were so profound that the bakufu decided to harness its benefits in order to allow the samurai class, who now existed in a time of peace, a method through which to express themselves, while simultaneously using this practice as a device of social control. Yet, little is known about the evolution of this practice and its reception between the first official accounting of blood revenge in the Azuma Kagami and the legalization of this practice under bakufu law. In this Master’s Thesis, I endeavor to bridge the gap in modern scholarship between the highly ritualized blood-revenge practices of the Tokugawa period and its origins in medieval Japanese history. To this end, I will explore the evolution of blood revenge practices in the sphere of social, political, legal, and cultural history by analyzing the first literary representation of the pioneering blood revenge incident in Japan – the revenge of the Soga brothers – in the Manabon Soga Monogatari and its later Tokugawa ehon adaptation.