China’s Warring States period, a raging dragon that would raze the land for 500 years, saw many kingdoms rise and fall, making way for the next generation of kings and generals to fight for supremacy. Eventually, seven powerful states emerged from the endless cycle of warfare. In the kingdom of Qin, Xin, a war-orphaned slave, trains vigorously with fellow slave and best friend, Piao, who shares his proud dream of one day becoming a Great General of the Heavens. However, the two are suddenly forced to part ways when Piao is recruited to work in the royal palace by a retainer of the King. After a fierce coup d'état unfolds, Piao returns to Xin, half dead, with a mission that will lead him to a meeting with China's young King, Ying Zheng, who bears a striking resemblance to Piao. Kingdom follows Xin as he takes his first steps into the great blood-soaked pages of China's history. He must carve his own path to glory on his long quest to become a Great General of the historic Seven Warring States.

Following the successful Sanyou campaign, the Qin army, including 1,000-Man Commander Xin, inches ever closer to fulfilling King Ying Zheng's dream of unifying China. With a major geographical foothold in the state of Wei now under its control, Qin sets its sights eastward toward the remaining warring states. Meanwhile Li Mu—an unparalleled strategist and the newly appointed prime minister of the state of Zhao—has taken advantage of Zhao's temporary truce with Qin to negotiate with the other states without interruption. Seemingly without warning, Ying Zheng receives news that armies from the states of Chu, Zhao, Wei, Han, Yan, and Qi have crossed into Qin territory. Realizing too late the purpose behind Li Mu's truce with Qin, Zheng quickly gathers his advisors to devise a plan to address the six-state coalition army on their doorstep. For the first time in history, the state of Qin faces complete destruction and must use every resource and strategy at their disposal to prevent themselves from being wiped off the map.

A year after the devastating battle against the formidable Zhao, the State of Qin has returned its focus to pursuing King Ying Zheng's ambition of conquering the other six states and unifying China. Their next target is Wei, a smaller state which stands as a geographic stepping stone for the sake of conquest. Xin, now a three hundred man commander of the swiftly rising Fei Xin Unit, continues to seek out lofty achievements in order to garner recognition for himself and his soldiers, motivated by those previously lost in battle. In the preliminary battles ahead of Qin's invasion of Wei, Xin finds competition in other young commanders who are of a higher social status than him. Back in Qin, the royal palace faces turmoil as opposing factions begin to make their move against Ying Zheng's regime. With their hands full both abroad and at home, Zheng and Xin must lead the way in this era of unending war, resolved to etch their names in history by creating a unified China.

Long ago, the king of Orvelia, Kyle, defeated the demon king Angmund and brought peace to the world. However, one hundred years later, demons have been sighted in the forests, threatening humanity once more. A scouting expedition is sent to verify the claim but only one member returns. Meanwhile, Riheet, the leader of a dark elf mercenary group, plots to take over Orvelia to exact revenge against the humans who forsook their race a century ago. The knight apprentice Kasel, accompanied by the priestess Frey, sets out to rescue Clause, an old friend who went missing in the tragic mission. However, along the way, Kasel discovers that he is the son of the revered King Kyle and the only one who can wield the Holy Sword Aea—the same sword that slew the demon king. To fulfill this destiny, the young knight must embark on a perilous quest, unseal the sword, and end the fear instilled by demons. As Kasel's journey to bring hope to humanity and Riheet's vow for vengeance intertwine, what fate could possibly await them?