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

He wrote The Mirror of War, The Book of Five Wheels, The Preface of Taidao Dao of Five Parties, and The Thirty-five Rules of the Art of War.

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