In 1535, Obayashi Kansuke, a masterless samurai, is on his way home to succeed his adoptive father after 15 years of journey studying military strategies. At a deserted village he drops in at, he saves a girl from a samurai. The samurai is one of the soldiers under Takeda Nobutora, the warlord of Kai, who are in the battle with the Imagawa clan of Suruga. The girl named Mitsu falls in love with Kansuke. Meanwhile, the Hojo family of Sagami invades the domain of Kai. Kansuke goes to watch the battle between the Takeda and Hojo armies. Though Kansuke has stopped her, Mitsu follows him and is caught by the soldier of the Takeda clan again.

Kansuke returns home in Mikawa Domain after 15 years. He brings the decapitated head of the samurai of the Takeda army he killed to save Mitsu—he have planned to show it as a display of his prowess in order to be taken into the service of the Imagawa clan. Coming back, Kansuke finds that his adoptive father now has a natural son. The father who wants the son, not Kansuke, to succeed him steals the head and tenders it to one of the warlords under the Imagawa clan as the son’s achievement. Kansuke decides to rename himself Yamamoto Kansuke, the family name of his real parents, and leaves Mikawa for Suruga, where his was born. In Suruga, Kansuke happens to know his elder brother Sadahisa is involved in a conspiracy against the head of the Imagawa family. For knowing the secret, Kansuke is attacked by a group of assassins directed by Sadahisa. Kansuke has to leave home again.

Kansuke goes back to the Kai domain, where he meets Mitsu. She is expecting a baby, whose father, she insists, is Kansuke. Though he refuses her once, Kansuke gradually becomes attached to the unaffected nature of the villagers and eventually makes up his mind to live there with Mitsu and the baby she is carrying. Meanwhile, the ruler Nobutora and his young son and heir Harunobu are on bad term. Nobutora wages wars one after another, provoking complaints against him among his retainers as well as common people. One day, Nobutora goes hunting to get nothing. Irritated, he shoots an arrow at a human—the woman aimed at is Mitsu.

Mitsu has been shot and killed by Nobutora. Kansuke keeps calm, but hearing Takeda’s retainers impose silence on the villagers about what happened, Kansuke attacks in fury at Nobukata Itagaki, one of Harunobu’s chief retainers. Though Kansuke is defeated, Itagaki gets impressed by his swordsmanship and tells Harunobu about the one-eyed man. Harunobu, who is also shocked by the cruel behavior of Nobutora, wants to see Kansuke. The two meet each other for the first time. Sensing Kansuke’s resentment against Nobutora, Harunobu persuades him to lay aside his grudge and hold ambition. Kansuke goes to Suruga on Itagaki’s order to spy into the Imagawa clan at internal strife. Kansuke informs Tadatane Ihara, his relative who is one of Imagawa’s main retainers, of the conspiracy against the clan leader. Ihara, however, tells Kansuke that the Imagawa leader as well as his brother has died mysteriously on the same day.

Kansuke is introduced to Jukeini, the mother of a potential successor to the late head of the Imagawa clan. Kansuke proposes the woman who has tremendous influence in the clan a plot to dispose of Fukushima, the betrayer who secretly communicates with Takeda Nobutora. Having no way to know that Jukeini’s son is working on amicable settlement with the Takada clan, Kansuke plans to take revenge on Nobutora for Mitsu when the head of the Takeda family comes to help Fukushima. Fukushima takes up arms against the Imagawa family but Takeda’s army does not turn up. Kansuke’s brother Sadahisa, who has been working under Fukushima, kills himself before Kansuke’s eyes.

Fukushima seeks refuge with Takeda’s retainer who introduced Fukushima to the head of the Takeda family. Nobutora kills both of the two. The conflict between Nobutora and his son Harunobu becomes more bitter after this. Meanwhile, Kansuke goes to see Jukeini’s son Yoshimoto, who now is the new head of Imagawa. Despite his achievements in disposing of Fukushima, Kansuke is refused to become a retainer of the clan. Kansuke’s hope to take revenge on Takeda with the help of Imagawa also disappears, as they are now in alliance. Kansuke departs for Sagami, the domain ruled by the Hojo clan, to look for a warlord to serve.

Kansuke is given a chance to talk to Ujiyasu Hojo, the head of the clan. However, Ujiyasu refuses to make Kansuke his retainer, sensing that Kansuke is driven by resentment against Takeda. Kansuke leaves Sagami and heads to Shinano. Meanwhile in Kai, Nobutora decides to conquer Shinano since the alliance with Imagawa enabled him to be off-guard about the southern border. In Shinano, Kansuke happens to meet again Heizo. Heizo is with his current master Sanada Yukitaka, who rules a small area of Shinano. The army of Takada leaves Kai and Harunobu also heads to Shinano for his maiden battle. At the news that Takeda’s troops are advancing on the Unnokuchi castle, Kansuke is sent to the castle as a messenger of Sanada.

The army of the Takeda clan besieges the Unnokuchi castle. Kansuke gives advice to the warlord of the castle and help him defend the castle from the 8000-person army. Harunobu Takeda has come to the battlefield for his maiden battle but cannot participate in the battle being deployed in the rear. After one month of struggle, Takeda Nobutora decides to retreat since his troops are about to run out of provisions and it has started to snow. The warlord of the Unnokuchi castle and his warriors are delighted to see the Takeda army leave. Kansuke advises them to keep vigilant but they start drinking believing that they have won. After a while, Harunobu returns with his 300-person troop.

Harunobu has taken the Unnokuchi castle by surprise. Kansuke appears in front of Harunobu, resigned to being killed. Harunobu puts his sword on Kansuke’s neck but leaves him alive, only declares that he has decapitated Kansuke. Three years later, Takeda allies with Suwa, a ruling clan of Shinano, and Harunobu’s younger sister Nene marries into the Suwa clan. Meanwhile, Nobutora openly shows his intention to expel Harunobu. Harunobu reveals to his right-hand man Itagaki that he is determined to oust the father from Kai.

Itagaki secretly works on persuading major Takeda retainers and the Imagawa clan to support Harunobu. Unaware of the conspiracy against him, Nobutora leaves Kai for Suruga invited by Yoshimoto Imagawa—the head of the Imagawa clan has chosen to side Harunobu and agreed to confine Nobutora in his domain forever. Kansuke, who has been in Suruga still masterless, is sent to bring Nobutora by order of Yoshimoto.

Harunobu declares in front of his retainers and his brother Nobushige that Nobutora is expelled. As the younger brother who was Nobutora’s favorite supports Harunobu’s decision, the retainers are united in aiding Harunobu as the clan’s new leader. Nobutora comes back from Suruga and sees Harunobu’s army is lined on the border. After a vain attempt to reenter Kai Domain, Nobutora realizes that he is expelled. Kansuke comes to take Nobutora to the capital of Suruga. On their way, the malice against Nobutora crosses on Kansuke’s mind. However, Kansuke’s anger dissipates when he sees Nobutora fall from a horse and show miserable senility.

Harunobu is now the leader of the Takeda clan. Kansuke has a masterless samurai attack Harunobu’s chief retainer Nobukata Itagaki and saves the retainer killing the samurai, for the purpose of becoming a retainer of Takeda. Itagaki sees through the plot but leaves Kansuke alive, remembering that Harunobu has once chosen to save Kansuke’s life. Hearing the incident from Itagaki, Harunobu calls up Kansuke in front of him and tells him to become his retainer, despite objections from other retainers.

Kansuke is challenged to a duel by the strongest retainer of the Takeda clan. Kansuke beats the samurai without an actual duel and makes Harunobu and the retainers appreciate his wisdom. Meanwhile, the second son of Harunobu loses his sight because of illness. Harunobu’s wife worries that this as an ominous sign of difficulties ahead brought by the one-eyed retainer. Harunobu takes no notice but her worry proves right—the powerful rival clan Uesugi starts invading Takeda’s land in Shinano.

Takeda’s territory in Shinano has been invaded by the Uesugi clan. Yorishige Suwa, Harunobu’s brother by marriage who has been allied with Takeda, makes peace with the Uesugi clan without consulting the head of the Takeda family. To design a plan to recover the land, Kansuke is sent to the Suwa region, where he first sees Yu, a daughter of Yorishige Suwa. Meanwhile in Kai, Harunobu chooses “furinkazan,” a quote from a military treatise written in ancient China, for new banners of his clan.

In April 1542, the first son is born to Yorishige Suwa and Nene, Harunobu’s sister. Kansuke proposes to Harunobu to secretly ally with a kin of the Suwa clan and launch a pincer movement, to regain the Suwa region without doing harm to Nene and the baby boy. Unexpectedly attacked by Harunobu, Yorishige Suwa is forced to be besieged in a castle with only a few retainers. Itagaki and Kansuke persuade the head of the Suwa family to surrender, saying Harunobu has no intention to destroy his family. Yorishige Suwa’s daughter Yu alone opposes taking Kansuke at his word.

Yorishige Suwa and Nene are sent to Kofu, Kai’s castle town, where the head of the Suwa clan is forced to kill himself. Kansuke goes to Suwa with Itagaki’s troops to make the remnants of the clan and the followers surrender. In the castle, Kansuke happens to find Yu. The princess has been refusing to follow her attendants’ persuasion to kill herself before she is insulted by the enemy. She yells out at Kansuke that she wants to be alive and see the world. Kansuke is instantly captivated by her noble beauty.

Kansuke decides to help Yu escape from captivity. Meanwhile, interested that Kansuke has saved the princess, Harunobu decides to take Yu as his own concubine, which is the only way to keep her alive. However, Yu feels hatred toward Harunobu, the very person who forced her father to kill himself. On her way, Yu is attacked by a masterless samurai and saved by Kansuke, who has come to bring her back, having learned of Harunobu’s decision. In order to turn Yu’s hatred from Harunobu toward himself, Kansuke tells her a lie that he, not Harunobu, sent the attacker.

Yu is brought to Kofu from Suwa and Harunobu declares that he will take Yu as his own concubine. The retainers bitterly oppose his idea. Only Kansuke sides with Harunobu, saying if a boy is born between the two and he becomes the head of the Suwa clan, Suwa’s people will swear loyalty the Takeda clan. Kansuke tries to persuade Yu but she rejects, saying she would rather kill herself than be a concubine of the man who caused death to her father. One of Harunobu’s retainers tries to compel Yu to commit suicide and Harunobu’s wife Sanjo flings harsh words at Yu.

Yu finally agrees to become Harunobu’s concubine. Harunobu holds a formal wedding ceremony for Yu to symbolize the ties between the two clans. Kansuke leaves for Shinano to devise a stratagem for further territorial expansion, believing that he has succeeded in prevailing on Yu to change her mind. However, Yu still carries a grudge against Harunobu and pulls a dagger on him.

In September 1543, Takeda’s army besieges Nagakubo Castle in Shinano. Harunobu decides to give Kansuke the position of Takeda’s military strategist, if he successfully captures the castle. With the help of the spy he has already sent into the enemy, Kansuke swiftly takes the castle. Meanwhile, Yu is in agony, torn apart between her affection and grudge toward Harunobu. Harunobu tells Kansuke to find out Yu’s true feelings.

Yu’s odd behavior sends ripples through the Takeda clan. Kansuke stands up for Yu and is accused by the senior retainers. Harunobu’s mother tries to admonish her but Yu just breaks down in tears. Harunobu decides to send Yu back to Suwa. Along the way to Suwa, Yu runs away. Kansuke manages to find her hiding in a small temple and hears her complicated feelings of love and resentment for Harunobu.

Yu becomes pregnant with Harunobu’s child. Kansuke is pleased as if it were his own. Meanwhile, Sessai, a military strategist of the Imagawa clan, visits Harunobu. Sessai asks him to send Takeda’s troops to Suruga based on the Takeda-Imagawa alliance, in order to help the Imagawa regain the territory that the Hojo clan has been occupying. Harunobu is skeptical about Imagawa’s true intensions. Kansuke is sent to Suruga to reconcile the Imagawa with the Hojo.

The Hojo clan is caught in a bind in their territory Musashi, as the strategic point Kawagoe Castle is put under siege by the army of Norimasa Uesugi. Kansuke goes to the castle, leading troops to help the Hojo clan, with another purpose in his mind—to persuade Yukitaka Sanada, who presently serves under the Uesugi clan, to be a retainer of the Takeda clan. Kansuke disguises himself and sneaks into Uesugi’s headquarters. Hearing from Kansuke that Uesugi’s troops are unvigilant and off guard, Ujiyasu Hojo decides to make a night assault against them.

Kansuke is wounded by gunfire in the night assault at Kawagoe Castle. He is saved by Yukitaka Sanada and stays at a temple in Kozuke, Uesugi’s territory, while the wound heals. Sanada makes up his mind to serve under Harunobu, the enemy of the Uesugi clan, but he faces stiff opposition from his wife and retainers. Meanwhile, Yu gives birth to a long-awaited baby boy, who is named Shiro. While in Echigo, the Nagao family seizes power and Kagetora Nagao, a younger brother of the head of the family, emerges as a powerful leader. Having returned to Kai and met baby Shiro, Kansuke finds a new purpose in life—aiding the son of Yu and Harunobu.

Kansuke devises a plan to make Shiro, the son of Yu and Harunobu, the next head of the Suwa clan. Toraoumaru, Yu’s half younger brother, has been regarded as the successor to the Suwa. In order to get rid of him, Kansuke goes to see Yoshimoto Imagawa and gets his approval to entrust Toraomaru to the Imagawa clan. Meanwhile, Harunobu enacts new laws for ruling his province.

Kasahara Kiyoshige, the warlord of Shiga Castle in Shinano, raises an army against the Takeda clan. Harunobu is irritated at being still unable to assume full control of Shinano. Takeda’s army advances on Shinano to capture the castle. Itagaki’s troop defeats the reinforcements sent by Kasahara’s ally. Although Kansuke proposes that Harunobu urge Kasahara to surrender, Harunobu commands his troops to behead the enemies and put the heads around the castle.

Having succeeded in capturing Shiga Castle by force, Harunobu declares war against Murakami Yoshikiyo, the warlord who dominates the northern part of Shinano. Kansuke tries to dissuade Harunobu but his efforts end in vain. Complains against continued battles increase in Takeda’s territory. Itagaki is anxious about challenging Murakami, the strongest warlord in Shinano, in such circumstances. Meanwhile, Amari, a chief retainer of the Takeda clan, goes to Shinano suddenly to meet Murakami. Amari says to Murakami that he will betray the Takeda clan in order to unify Kai.

In February 1548, Takeda’s troops advance on Shinano. The vanguard led by Itagaki and Amari battles against Murakami’s troops in Uedahara. Itagaki is ready for death and tells Kansuke to be a real military strategist and protect Harunobu. On the night, Amari defects to the enemy, as he promised with Yoshikiyo Murakami. Hearing this, Harunobu is outraged but Kansuke perceives that Amari is just pretending to be a traitor. As Kansuke infers, Amari tries to kill Murakami, but fails and is caught. Meanwhile, Itagaki’s troop is surrounded by Murakami’s army, having chased the enemy too far against Harunobu’s command. Although Takeda’s troops battle with all their force to save Itagaki, he dies on the battlefield.

In the battle at Uedahara, the Takeda clan has lost two generals—Itagaki and Amari. Though he at first refuses to admit his defeat, Harunobu decides to retreat in the end. In Kai, Harunobu repeatedly asks himself why he lost. Revolts against the Takeda clan break out in various areas and Kansuke is busy to contain them. The Ogasawara clan, a feudal lord of Shinano, seizes the occasion and invades Suwa. Owing to Kansuke’s tactics and preparations by Itagaki, who had foreseen the situation, Takeda’s army defeats the troops of Ogasawara.

Around the same time that Harunobu and Kansuke defeat the Ogasawara clan, Kagetora Nagao becomes the head of the Nagao family, succeeding his elder brother. Things finally calm down in Shinano. Kansuke goes on a trip to obtain guns, foreseeing that the new weapon is the key for future victories. Coming back to Kai, Kansuke tells Harunobu about his grand plan of seizing control of Echigo, Suruga, and then the whole country. Kansuke asks Harunobu to let him infiltrate Echigo to spy on their potential enemy.

Harunobu finally conquers the Ogasawara clan and seizes their territory in Shinano. His only great enemy of Shinano, Murakami, remains. Capturing the impregnable Toishi Castle is the key in defeating Murakami, and Sanada who used to preside over the territory takes on the important task. Although Sanada is eager for take action, Kansuke dissuades Sanada foreseeing it as premature. Kansuke infiltrates to Echigo to ascertain Kagetora Nagao's caliber. Meanwhile, Sanada plots the invasion of the castle against Kansuke's admonition.

Kansuke disguises as a gun trader and meets Kagetora. He offers Kagetora 10 guns, but he demands to provide 100 guns, saying he will take Kansuke as a hostage until he meets the demand. Although Kagetora is almost certain that Kansuke is the general of the Takeda clan, Kansuke has no intention of responding to Kagetora's demand and is pleased to become a hostage, taking the advantage to spy on the Nagao family. Kagetora takes him to Usami's castle, a neutral warlord in Echigo, whom Kagetora hopes to win him over to his side. Meanwhile, Harunobu advances on Murakami to capture Toishi Castle and suffers an unexpected crushing defeat.

Kansuke's disguise as a gun trader does not deceive Usami. Kagetora entrusts Kansuke to Usami, as an indication of Takeda's plot to seize Echigo and make Usami realize the importance of unifying Echigo. Usami understands Kagetora's intention and decides to serve the Nagao family. Meanwhile, Kansuke is unable to meet Kagetora's demand and is set to be executed.

Harunobu saves Kansuke and goes back to Kai. During his absence, the Takeda clan was severely defeated by Murakami and Sanada, the very person who caused the defeat, is under fire from the retainers of the Takeda clan. For Sanada to wipe the disgrace and survive, he must succeed in capturing the impregnable Toishi Castle. Kansuke initiates Sanada a secret plan—to persuade Takanaga Tokita, Sanada's younger brother who presently serves under Murakami, to become a retainer of the Takeda clan.

Hara, Takeda’s retainer, suddenly introduces his daughter Ritsu to Kansuke to be his wife. Ritsu’s passionate approach to Kansuke appalls him. On the way to Suwa to visit Princess Yu, Kansuke encounters a suspicious group escorting a beautiful princess, Ogoto. Having heard from Ritsu that Harunobu will receive a new concubine, Kansuke links the princess as the new concubine. Yu is jealous of Ogoto and anxious about her son Shiro’s future which might be threatened by Harunobu and should Ogoto bears his child.

Kansuke, prepared to kill Ogoto on behalf of Yu, loses his motivation, recognizing her innocence and beauty. Instead, he advises her to respect Yu’s son Shiro as the successor of the Takeda clan. On New Year’s Day in 1552, Oyamada, Takeda’s general, is killed by his concubine, Miru. She had long felt resentment toward the Takeda clan for her husband, Sasahara, was killed by them.

As Harunobu’s mother senses that her death is near, she is concerned about Harunobu’s future and entrusts Kansuke with Harunobu. Meanwhile, the army of Norimasa Uesugi is driven into a corner by Ujiyasu Hojo, whose family dominates the Sagami and Musashi regions, and Uesugi runs for Echigo seeking Kagetora’s assistance. Meanwhile, Kansuke proposes to Ujiyasu a three-line alliance: Takeda, Imagawa and Hojo.

After strengthening the tie with the Imagawa family by the marriage of Imagawa’s daughter and Harunobu’s son and heir Taro, Takeda’s troops finally advance on to Shinano defeating Murakami. A well thought-out strategy by Kansuke causes the feudal lords of Shinano to surrender to the Takeda clan without a battle one after another and Murakami instantly becomes isolated. Foreseeing a no-win situation, Murakami runs to Kagetora in Echigo. Kagetora makes up his mind to advance on to Shinano to restore order, having learned of Takeda’s villainous plot from Murakami.

In August 1553, the troops of Echigo led by Kagetora advances to Kawanakajima of Shinano and the first battle of Kawanakajima breaks out. Foreseeing that Kagetora’s target is to behead Harunobu, Kansuke counterplots by not fighting back but instead drags Kagetora south. Usami, a general of the Nagao family, detects Kansuke’s plot and shifts their course toward Fukashi Castle, Tadeda’s strategic point in Shinano, for the purpose of decoying Harunobu towards the battle field.

After the first battle against Kagetora, Harunobu visits Yu in Suwa. Having heard that Kansuke might marry Ritsu, Yu has mixed feelings. Meanwhile, Kansuke embarks on the three-line alliance among Takeda, Imagawa and Hojo, while Kagetora heads for the capital, Kyoto. The year after, Harunobu, Yoshimoto, and Ujiyasu gather at Zentokuji Temple in Suruga to confirm their alliance.

Yu falls ill and tells Kansuke that her death is near. Kiso is chosen by Yu for Kansuke's next conquest. On the day Kansuke is to leave for Kiso, Yu urges him to get married as soon as he comes back, which he promises to do. While Kansuke and Harunobu are invading Kiso, the troops led by Kagetora also advance to Zenkoji Temple.

Yu passes away before Kansuke comes back from the battle. He remembers her last words urging him to marry and leave an heir. Kansuke leaves a note to Harunobu and goes on a trip to shake off his unsettling mind. Meanwhile in Echigo, unified by Kagetora, conflicts over the territory between the ruling families continue as a result of the long drawn out battles. Kagetora is disappointed with the quarrels among his retainers and suddenly disappears from Echigo.

Kansuke decides to adopt Ritsu instead of marrying her. Harunobu succeeds in persuading Nagao's chief retainer to take on Takeda's side. Harunobu gaining momentum advances on to northern Shinano, to obliterate Nagao family's influence. Although Kagetora also leads his troops forward, Takeda's troops avoid armed confrontation. The battle between Takeda and Nagao comes to an end by the order of Shogun Yoshiteru Ashikaga. Harunobu accepts the order in exchange for becoming a federal lord of Shinano. He declares that he will enter priesthood and changes his name to Shingen. Kansuke follows and changes his name to Douki.

Usami, a general of the Nagao family, sends Heizo to Suruga to see Toraoumaru, Yu's half brother who is also the bereaved child of the Suwa Family. Heizo and Toraoumaru, harboring resentment against the Takeda clan, infiltrate to Kai. Having heard that strange young monks are seen around Shingen, Kansuke is suspicious.

Usami's assassination attempt on Shingen fails. Kansuke's mistrust fuels towards the Imagawa clan in spite of the alliance between Takeda and Imagawa. In 1560, Yoshimoto decides to head for the capital, Kyoto. He sends his troops to Owari which is under the control of the Oda Family. Kansuke starts plotting a new scheme for if Oda wins, it would be an excellent opportunity for the Takeda clan to seize Suruga.

In 1560, Kagetora advances onto Kanto defeating Hojo in order to restore the Kanto area. Around the same time, Yu and Harunobu's son Shiro celebrates the coming of age and assumes Suwa's surname. Warlords of Kanto gather around Kagetora to take his side which soon numbers to 100,000 forces. Usami fears Kagetora's arrogance. The troops led by Kagetora surrounds the impregnable Odawara Castle, the strategic point of the Hojo clan. Kagetora decides to take over as the head of the Uesugi Family, and changes his name to Masatora Uesugi.

Masatora realizes that his failure in capturing the Odawara Castle was due to his arrogance. He reaffirms his determination for the next battle against the Takeda clan. Sensing that the decisive battle is near, Kansuke urges his adopted daughter Ritsu to marry. In August 1561, the Uesugi clan's 13,000 troops head to Kawanakajima in Shinano.

After hearing an old woman's prediction that thick fog will descend in Kawanakajima the following morning, Kansuke decides that the time has come for him to make the move. Kansuke divides Takeda's troops into two forces―8,000 main forces led by Shingen to wait at the mountain foot and the other 12,000 forces to attack Uesugi's troops on the mountain from the rear. However, the attempt to trap the enemy had been foreseen.

On September 10, 1561, the fierce battle between Takeda and Uesugi rose to its peak. Kansuke's strategy was foreseen by Usami and Uesugi's troops led by Masatora attacks Takeda's main forces. Shingen loses his brother and a general and Takeda's troops were on the verge of destruction. While Shingen waited for another force of 12,000 to arrive for support, Kansuke decides to attack the enemy himself to protect Takeda's main forces.