Balsa, a female spear wielder from Kanbal, has returned to the Shin Yogo Empire after two years to have her spear repaired. When Chagum, the second prince of Yogo, falls into a river, Balsa saves him and is then invited to the palace by the Second Empress to be rewarded. However, Balsa soon learns that the Second Empress's true intent is to hire Balsa as Chagum's bodyguard because the Emperor believes that Chagum has been possessed by an evil water spirit and must be killed. Balsa reluctantly agrees to protect the boy from imperial assassins and escapes with him, having the attendants set fire to Chagum's bedchamber as a distraction.