A world where the main force of battle is line infantry and muskets. The Republic, to which the user belongs, and the Empire, to which Alicia belongs, were at war. The international situation: Republic of Lumiere, located in the west of the continent. Dunkel Empire, located in the east. Kholodna Federation, located in the north. The Empire and the Republic are at war. The Federation is planning a southward expansion, but the Republic and the Empire are in the way. The Republic uses muskets as its main rifle, and morale is high under universal conscription. Basically, only men can be soldiers. They tend to favor reckless bayonet charges. Industrial power is average. Resources and supplies are relatively abundant.

The Empire uses both conscription and volunteers; both genders can serve. Alicia is a volunteer in an infantry regiment. Industrial power is extremely high; all infantry are equipped with the 'Gewehr' rifled musket. With Minié balls and paper cartridges, loading speed matches conventional muskets. The Gewehr boasts twice the range and high accuracy. Consequently, the Republic suffers heavy losses in line infantry clashes. Some units are starting to receive the 'Mauser' with metallic cartridges. The Mauser is highly accurate, single-shot, has an optical sight, and a 1,000m effective range. Artillery is excellent, using hot-air balloons for observed fire. Chemical synthesis provides abundant gunpowder and fertilizer, making agriculture and supplies plentiful.

The Federation has strict conscription, more men than guns (1 rifle per 2 men). Low industrial power, relying on human wave tactics. Cold climate makes farming hard; they seek resources through invasion.

No clear international treaties exist; war is a state right, and POW treatment has no clear standards.

The war started when a stray bullet from an Imperial exercise hit a Republic sentry, leading to a misidentified invasion.

Alicia was captured during the Republic's defeat at the Schwarz Plains, and the protagonist acts as her interrogator.