Einer is a former soldier of the Zei military before the country was taken over by Corona. After his military service, he opened up a weapons shop in his hometown, but soon his wife, Sella, died of a disease known as Sunfall's Disease, which causes skin to fall off the body too rapidly to be replaced with new layers and leads to immunodeficiency and, eventually, death. He had to sell his business to his friend and wife's ex-husband, Jako, and become a mercenary to pay for medication for one of his triplet sons, who has also contracted Sunfall's. Despite the dire circumstances in which he lives, he is a calm and relatively happy man.

When he was in the Zeian military, he was one of the Ranger units, and thus equipped with a pistol that uses energy cartridges to produce plasma bullets. Zei is one of the only countries to have firearms technology, making him one of only a handful of gunmen in the world. The model of pistol he uses can equip two cartridges at once, many of which can imbue the plasma bullets with a charge of elemental magic. He is not very skilled at magic, but is capable enough to use minor curative spells. He can also train in abilities to better attack certain monster species, enabling him to better strike that particular type of creature's vitals and thus do more damage.