More than a decade after his legendary duel with Sasaki Kojiro on Ganryujima Island, a forty-four-year-old Miyamoto Musashi travels with his adopted son Iori, accepting an invitation to stay as a guest in the household of a feudal lord. As he settles into this period of relative calm, Musashi takes stock of his life and the countless battles that have shaped his path. He becomes involved in putting down the Shimabara Rebellion and takes on the instruction of younger students seeking his guidance. However, the past refuses to fade quietly; a former disciple of his slain rival, Kojiro, begins stalking Musashi, driven by a burning desire for revenge. This narrative unfolds across the manga's two volumes, exploring the legendary swordsman's later years as he grapples with his legacy while still facing the consequences of his violent history.

The story follows Musashi during this reflective period as he accepts a position as a guest of the Hosokawa clan in Kumamoto. Encouraged by the domain lord, he decides to commit his life's philosophy and martial strategy to paper, retreating to a cave known as Reigando to focus on his writing. Even as he is beset by illness, Musashi perseveres in composing his masterwork, The Book of Five Rings, the famous text on strategy and swordsmanship. This act of creation runs parallel to the final resolution of his long-standing vendetta with the legacy of Kojiro, as the grudges of the past finally come to a head. The series concludes with Musashi's death, presenting his final days not as a simple decline but as a last demonstration of his principles and the ultimate closing of his life's complex circle.