Conversation so far:
what was first duel for Miyamoto Musashi?
According to the introduction of The Book of Five Rings, Musashi states that his first successful duel was at the age of 13.
what was special about the first duel of Miyamoto Musashi?
against a samurai named Arima Kihei who fought using the Kashima Shintō-ryū style, founded by Tsukahara Bokuden
did Miyamoto Musashi duel with anyone else after Arima Kihei?
He spent his time traveling and engaging in duels, such as with an adept called Akiyama from the Tajima Province.

Question: who else did he fight?
Self-contained rewrite: who else did Miyamoto Musashi fight after Akiyama?