Expelled from the Mutenichi-ryū sword school in 1732 for violating its forms with improper techniques and a foreign sword while defending his master against bandits, Saburō Anotsu forged a lasting grudge against the school, particularly the Asano family. This deep resentment defined his later life, leading him to abuse his grandson, Kagehisa Anotsu, forcing harsh training and instilling profound disillusionment with traditional samurai concepts like honor and good form. He taught Kagehisa that victory demanded any means necessary.

Saburō's influence directly drove Kagehisa to establish the Ittō-ryū, a school prioritizing lethal practicality over rigid forms. Decades after Saburō's expulsion, Kagehisa led the Ittō-ryū to destroy the Mutenichi-ryū dojo, killing its head Kurose Asano (son of Saburō's fellow student Takayuki) and Kurose's wife, Otoki, as vengeance for his grandfather's disgrace. Saburō also mentored swordsmen like Sabato Kuroi, a core Ittō-ryū member who participated in the Asano dojo massacre and taxidermied Otoki's head as a trophy, reflecting the brutality rooted in Saburō's teachings. Saburō's personal grievance thus perpetuated a cycle of violence, defining the Ittō-ryū's conflict with the Asano lineage through his enduring ideological impact on Kagehisa and the school's ruthless ethos.