Yes, Musashi Miyamoto was a real swordsman and strategist from the end of the Warring States Period to the beginning of the Edo period.

He is the author of The Mirror of the Military Way, The Book of Five Wheels, The Preface of Five Sides of Taidao, and Thirty-five Articles of the Art of War by Sun Tzu.

However, whether his opponent Sasaki Kojiro really exists is still inconclusive in Japanese history.