Taught in the martial skills of his father, Soodol vows to kill any Japanese invader he encounters. But the Joseon dynasty, after two centuries of peace, is unprepared, naïve and corrupt. The army from over the sea is the result of a century of civil strife and is arguably the most efficient killing machine ever. Government armies are swept aside or run away. Only the numerous guerilla 'righteous' armies are keeping the enemy in check on land by harassing foraging parties.

Too lowly to be part of a government army, Soodol is enticed to join a righteous army with his new monk friend, Hong, where he hopes to find camaraderie and acceptance. The guerillas' success earns them a new, dangerous foe, however. An elite samurai, one of Japan's finest swordsman, vows to destroy the righteous army and spearhead a path into Jolla, the breadbasket of Joseon. Soodol may be the only man in Joseon who can face him, and survive.