The film mainly follows the famous 1597 Battle of Myeongryang during the Japanese invasion of Korea 1592-1598, where the iconic Joseon admiral Yi Sun-sin managed to destroy a total of 133 Japanese warships with only 13 ships remaining in his command. The battle, which took place in the Myeongryang Strait off the southwest coast of the Korean Peninsula, is considered one of the greatest victories of Yi.

In 1592, admiral Yi Sun-sin and his fleet face off against the might of the invading Japanese navy and its formidable warships. As the Korean forces fall into crisis, the admiral resorts to using his secret weapon, the dragon head ships known as geobukseon, in order to change the tide of this epic battle at sea.

The Imjin War reaches its seventh year in December of 1598. Admiral Yi Sun-shin learns that the Wa invaders in Joseon are preparing for a swift withdrawal following the deathbed orders of their leader Toyotomi Hideyoshi. Determined to destroy the enemy once and for all, Admiral Yi leads an allied fleet of Joseon and Ming ships to mount a blockade and annihilate the Wa army. However, once Ming commander Chen Lin is bribed into lifting the blockade, Wa lord Shimazu Yoshihiro and his Satsuma army sail to the Wa army’s rescue at Noryang Strait.