In June 1592, one month after the
sea battle at Sacheon,
daimyo Wakisaka Yasuharu arrives at the Japanese naval base in
Busan to take charge of the fleet and counter the threat posed by
Joseon commander
Yi Sun-sin. From some terrified survivors of the battle, he learns of
a new, fully enclosed Joseon battleship which they have dubbed
bokkaisen (after a sea monster from Japanese mythology) and
mekurabune ("blind ship"). However, that engagement has revealed some critical flaws in its design, such as the fixed dragon head at its bow being prone to getting stuck after making a ramming attack, and its weaker flank armor. Wakisaka agrees to join forces with the rest of the Japanese navy to ensure a decisive success in their
campaign to conquer Joseon and, from there on,
Ming China. At the Left Jeolla Navy base at
Yeosu, Yi assembles the Joseon admirals for a conference about their upcoming naval operations.
Won Gyun, commander of the Western Fleet, argues for a defensive stand rather than a preemptive strike, and after the Japanese sacking of
Pyongyang and
the king's flight to
Uiju becomes public knowledge, other commanders begin to agree with him. After dreaming about his time as a cavalry general against the
Jurchen, Yi devises a new strategy which he names "Crane Wing", a crescent-shaped formation designed to trap the enemy from three sides. He also gains the respect of Junsa, a
samurai captured at Sacheon after he had wounded Yi with an
arquebuse shot. However, after identifying and following one of his agents, a troop of Japanese spies discover Yi's base, free their imprisoned countrymen, damage the turtle ships with fire, and escape with their construction plans. Yi hurries to
Suncheon to meet with the vessel's inventor,
Na Dae-yong, who is working on an improved version, and declares that he will not use the turtle ships in the next battle, knowing that Wakisaka will discover and exploit their flaws. After learning of Yi's intended strategy from the construction plans and Junsa's testimony, and upon receiving reinforcements from
Katō Yoshiaki (Wakisaka's fiercest rival) and
Kuki Yoshitaka with sturdier, armored ships and cannons, Wakisaka decides to go on a two-pronged offensive by land and sea against the Left Jeolla Navy headquarters. Two of Yi's spies, Lim Jun-young and Jeong Bo-reum, are discovered, whereupon Wakisaka expels Kato and Kuki from the alliance and seizes their ships and weapons before setting out to set an ambush for Yi at the strait of Gyeonnaeryang. While Lim escapes on his own, Junsa, who has finally switched his allegiance, helps Jeong convey Wakisaka's plans to Yi. He then tries to alert
Jeonju, the fortress covering the land passage to the naval base, but is captured by members of Joseon's
Righteous Army. Even though his warning is met with scepticism, Hwang Bak, the militia's commander, decides to secure the pass and invites Junsa to fight by his side. Upon being informed of Wakisaka's movements, Yi decides to lure him into the open waters at nearby
Hansando. When the Joseon fleet arrives at the strait, commanders
Eo Yeong-dam and Lee Un-ryong act as bait; when that fails, Yi sets out with the whole fleet, prompting Wakisaka to attack. When Won Gyun's negligence grants the Japanese a breach to charge through, Yi deploys the turtle ships, which he has held in reserve on Na's insistence. After Wakisaka' forces disable them, Yi sends in the improved turtle ship, enabling Eo and Lee to rejoin their lines and complete the Crane Wing. Finally caught in Yi's trap, Wakisaka's fleet is shot to pieces. Wakisaka's last-ditch attempt to ram Yi's flagship is foiled by the new turtle ship, and he is wounded by an arrow from Yi as he abandons the ship. On land, the Righteous Army is reinforced and successfully holds the pass, though Hwang Bak dies in battle. Following this, Yi continues his campaign for a while and attacks
Angolpo and
Busan, forcing the Japanese to suspend further naval operations, before retreating back to his base. One year later, Yi erects a new base on Hansan Island, the site of their greatest victory up to that date. == Cast ==