At the fights with Yoshioka, Musashi ignored the proper procedure of musha-shugyo (swordsman's training) and ill-manneredly issued a challenge, so a fight of one versus one expanded into a small battle, and at last, unfortunately Yoshioka was beaten and even the family and school ended.
吉岡家の断絶は、武蔵が当時における、武者修行の礼儀を無視した形で勝負を挑んだため、さながら小規模な合戦にまで勝負の規模が拡大し、吉岡がそれに敗れてしまったためである。