There Will Be One - The Windshine Chronicles, #2

For generations, Windshine has chronicled the exploits of young men on quests to become heroes. Most suffered brutal deaths, and distrust of the Dark Elf grew until rogue officials offer sixteen-year-old archer, Woo Jin, the chance to eliminate her. If he succeeds, they will name him hero. If he fails, he can never return home. In the company of musicians, veterans, and the wielder of the glyph blade, Woo Jin sails from Jeju to the mainland.
Their quest- to evacuate Goseong, the village of children, from the devastated borderlands of South and North Hanguk. Unbeknownst to Woo Jin's companions, he studies Windshine for weaknesses even as he wonders what evil lurks in the Dark Elf. Reaching the village, the companions encounter a fierce horde of northern soldiers. Battling to survive, Woo Jin spots the perfect opportunity to fulfill his mission, but will he assassinate the Dark Elf to become a hero?