Yi Sun-sin is a hero worthy of any nation. He demonstrated the best qualities of the Korean person; qualities that find their root in Korean Confucian philosophy.
Yi made outstanding contributions to naval military strategy. Actually, his use of the Turtle ship had a parallel on the other side of the globe. At about the same time, Sir Francis Drake used his fire ships to disorient and overwhelm the Spanish Armada. Yi used the Turtle ship as a fire ship, except the Turtle ship survived to fight another day while Drake's fire ships burned in the attack. Still, both Yi's and Drake's strategies had the same effect; they disoriented a superior naval force and annihilated them.
Yi's courage and leadership are epic as well. He not only faced a determined foe in the Japanese navy and army, he had far fewer ships then his enemy. Koreans, historically, are not a sea-faring nation. Historically they have conducted little of their trade by water and have little experience with the sea, other than fishing. Yet, Yi's navy fought battles renown for their strategic genius. His genius, alone, does not account for the loyalty and cohesiveness he created among his sailors. That came from his strength of character; Yi embodied the Confucian gentleman.
He best displayed his Confucian virtues when court intrigue forced him into prison and disgrace. Rather than rebel, he accepted his punishment, enduring the humility of prison and being stripped of his rank. When released through intervention of government officials who knew his innocence, Yi insisted on reentering the ranks as a common soldier, even though Hideyoshi's army's devastated the country while he stayed on the sidelines. Once reinstated, Yi fought with the remnants of a defeated navy, leading the few ships in his command to triumph over Japanese fleets once again.
Yi is a hero for all ages. Koreans rightly praise his talent and his virtue. Even Japanese leaders who fought against him, praised him. The true measure of a person is how their enemies see them. In that regard, Yi stands as a giant, just as his statue stands fearless in the center of Seoul