Born into a kendo family, the boy Musashi inherits his late father's passion for the sword and trains hard every day. Through his friendships with the neighborhood children and an encounter with a puppy, Musashi takes his first step as a swordsman.

On a snowy night, Musashi is attacked by a dog and hospitalized with injuries. His pet dog Juichi is also hurt while protecting him. His parents' deep love as they pray for his recovery, and a fateful bond with a powerful rival he meets in the hospital, spur Musashi's growth as a swordsman.

A boy arrives at a kendo dojo and challenges the adults to practice with him. Putting on armor for the first time and facing a serious match, the boy grows little by little through kendo.

Musashi is pestered by the kindergarten bullies, but he beats them all and is recognized as their new boss. Later, walking his dog along the river, he meets a big man taking a nap in the sun: Iwao Oishi.

In practice with Iwao, Musashi cannot land a single strike. Crushed by frustration, he nonetheless glimpses the depth of kendo in Iwao's words and movements, and vows to grow further.

Musashi meets a strong rival, Yonai, at a kendo tournament. Shocked by Yonai's overwhelming strength, Musashi still shows the fruits of his daily training, winning match after match as he charges toward a showdown with his rival for the title.

In the final of the kendo tournament, Musashi faces a beautiful young swordswoman. With their abilities evenly matched and a fierce exchange unfolding, the match is carried into overtime.

Musashi trains hard, holding a rematch with his rival in his heart. He shows overwhelming strength at the promotion exam, but is not satisfied with the rank he is given. The instructor tells him that the way of the sword is not bound by rank — it is about defeating oneself.

Musashi takes on a challenge set by a certain man: defeat the Four Heavenly Kings, the four strongest grade-schoolers in Morioka. Disguising himself, he sets out and beats the strong opponents one after another.

Oishi shows Musashi the dents left in the wall by generations of club members ramming it with their face guards, telling him they are proof of relentless daily practice. The mark Musashi has left is still small, and Oishi says sternly: "Your sword is worth no more than that."

Musashi's father wins the All-Japan Kendo Championship. The joy is short-lived, though, as a letter arrives from his father's university senior — Kunihiko Todo, a man who once conquered all Japan at the youngest age ever. And Todo has a son the same age as Musashi: Shura.

Musashi is astonished by the extraordinary talent of Shura, the boy he meets at the dojo. The two young swordsmen acknowledge each other's strength, and learning of their fathers' past, both burn with even more drive to practice.

In a dream, Musashi undergoes fierce practice with Shura. Reunited with him in reality, the two speak of their feelings about kendo, and as each watches the other's father's harsh training, they are pushed forward as swordsmen.

Musashi faces the death of Shura's mother — who was also his own father's younger sister. Around her death, complicated feelings intertwine among the family and relatives. Musashi and Shura each have their own path of the sword and their family bonds put to the test.

Learning of his father's burning devotion to kendo, Musashi resolves to devote himself to the way of the sword as well. But his mother's new challenge and his school life keep standing in his way.

Over summer vacation, Musashi forces his way to Eiichiro's side and begs to be trained in kendo. He is refused at first, but Musashi refuses to leave the dojo. In time he touches the very essence of Eiichiro's midnight training, and grows as a swordsman.

Musashi trains hard alongside Shino — waterfall austerities, rabbit jumps and more. But Shino tells him that tomorrow will be the last day they can practice together. Shaken, Musashi grabs his practice clothes and runs off, beginning solitary training in a graveyard.

Having mastered footwork through harsh training with his father, Musashi returns from his mountain retreat to school life — and meets a new strong rival, Kawaguchi. Kawaguchi taunts him that without a stick he cannot even fight, and Musashi flies into a rage.

Musashi's father fights a bitter battle against a powerful rival at a kendo tournament and wins brilliantly. Deeply moved by his father's strength, Musashi looks ahead to his next goal: making his mark at the national tournament.

While Musashi trains hard at the dojo, he is reunited with Shura. Through practice the two feel each other's growth and deepen their friendship. Before long, on the stage of the All-Japan Kendo Championship, the bond and the grudge between their fathers come to light.