Due to the long war, the Muromachi shogunate gradually declined. The world has entered the secret realm of mountains and seas during the Warring States Period, which advocated blood debt and blood repayment. Deep in the dense forest of the Kingdom of Nori, there is a gun group with the Yatagarasu as its military flag and emblem. They work as mercenaries and gallop on the battlefield, and their name is "Zahe Zhong". The person who inherited the title of leader of the Zahe clan was named Sun Yi, and he was a young man who drifted here from a foreign country. On the other side, Saburo, who was the first to notice the aggressive intentions of European powers, was running around to protect Japan. The two people who had nothing in common first became connected due to the attack of foreign invaders. How will this group of men in the Warring States Period implement their beliefs and justice. Their story officially begins——!