Book of 5 Rings - Wind Book
The wind Book describes other schools of martial arts in Musashi's time. He is generally dismissive. They have different weapons and techniques. the key point he makes is that longer or shorter swords are fine, but relying on them or preferring them is not the way.
Musashi advocates knowing and using all weapons and preferring none. Although Musashi is famous for his two sword technique, several times in the 5 Rings, he explain as when it is better to use a single, long sword or short sword.
Also in the Wind Book, Musashi advises against developing unusual stances or hand techniques. to Musashi these are distortions of correct stances and the beginning of defeat. After all, the point is to get your opponent to be off balance while you maintain the balanced position. Always preserving the balances mind and body of a true strategist is Musashi's preoccupation.
17th Century Japanese Firearm
Perhaps the greatest example of Musashi's style was in his most famous fight with Sasaki Kojiro. Sasaski was known for his very long sword and technique. Both swordsmen were considered unbeatable. A match was arranged with Musashi at a local beach. Musashi slept in. When awoken, he rinsed his face, wrapped his hair in a towel and got on a boat to go to the site of the duel. While in the boat he used his knife to fashion a bokken , from one of the oars (how he negotiated this and what the ferryman said about his strange behaviour is not recorded). Arriving quite late, Musashi bowed to Sasaki and struck a fatal blow with the bokken. Musashi's towel fell off. It had been cut off by Sasaski's sword, barely missing Musashi's face.
The controversy continues today. Arriving late is just not on in Modern or ancient Japan. Was this then as fair fight? To a peacetime, armchair samurai? Probably not.
15th Century Japanese Sword blades.
Looking at the Five Rings we get a different perspective.
That Musashi slept in and his casual attire shows his mind was unaffected by his impending fight.
Also Sasaski relied on his weapon of choice and had no answer when Musashi showed up with something different. Musashi probably could have won using his tried and tested two sword technique, but he was not overly attached to using two swords even thought it had made him famous.
That Sasaki was able to cut Musashi's towel, but not his face shows Musashi's skill at judging his opponent's reach, allowing Musashi to close in to inflict maximum damage while maintaining a safe distance.
Also Sasaski thew away his scabbard just before the duel. Most commentators take this as a sign that he knew he was beaten before the fight. Musashi explains repeatedly that the psychological victory is as important as the physical one. Sasaski had been disturbed by Musashi's tardiness, manor and weapon of choice to the point of losing sight of victory. Lastly, to Musashi, turning up when expected in the style that is expected and the weapon that is expected is an anathema.
Similarly, getting flustered because the enemy arrived late is a serious fault on the part of the strategist. History is full of wars that we lost by people whose defence was "the other side didn't fight in the expected way". Japan was to learn this lesson 200 years later when Perry turned up in his black ships outclassing Japan's dated military methods and equipment. To the samurai, Perry was not following the rules. Musashi would have understood.