Johan Anderson, a high school teenager in Japan, along with his classmates, is suddenly summoned to another world by an empire that needs a hero to win the war. Each student gets a job that determines their abilities, but Johan gets a job that seems strange and useless: 'Modern Soldier'.
Johan's personal soldiers, who had loyally served him from the beginning, were granted a full week of leave. They returned to Duke Arganus' southern lands, their homeland, to rest and regain their strength. Johan understood that his troops also needed time to recover after the brutal battle against the rebels. Even though the modern technology they wielded gave them a significant advantage, war still left scars—both physical and mental.
After a week had passed, the soldiers returned to the headquarters in Eas, the capital of Althuria. Upon arrival, they were met with an unexpected sight: waves of new recruits. Many were eager to join the First Army, a new military force established by Johan to protect the kingdom from various threats. This force was different from the traditional armies of the kingdom. They were trained with modern military methods and used firearms as their primary weapons, something that had been previously unheard of in this world.