According to "Gorin no sho," at the age of thirteen, Musashi fought his first duel with Kihei ARIMA of Shinto-ryu School and beat him; at the age of sixteen, he beat a strong heihoka, Akiyama from Tajima Province; until the age of twenty-nine, he fought over sixty times and beat every opponent.
『五輪書』には13歳で初めて新当流の有馬喜兵衛と決闘し勝利、16歳で但馬国の秋山という強力の兵法者に勝利、以来29歳までに60余回の勝負を行い、すべてに勝利したと記述される。