In a world without a Third World War or alien invasion, the battle story paints a picture of daily life where robots are an integral part of society, contributing in various ways. Standing at just 15 centimeters or about 6 inches tall, "Shinki" are miniature partners designed to assist humans. Brimming with intelligence and emotions, these Shinki are solely devoted to serving their "Masters" and are armed with weapons and armor, engaging in battles with each other as "Busou Shinki" or "armed divine princesses." Masato, a freshman in high school, is accompanied by three Shinki - Ann (Arnval), Aines (Altines), and Lene (Altlene) - who are all dedicated to serving him. However, the arrival of the aggressive Strarf throws things off balance.