A young woman with amnesia must hunt down the people responsible for her brutal and bloody past to find the truth of her lost identity.

As humanity's war with the Neuroi—a mysterious, hostile alien race possessing weapons of unparalleled power—continues being fought across Europe and Africa, a new fighter squadron is formed. The 502nd Joint Fighter Wing, also known as the Brave Witches, operates on the eastern front, scouring the icy vastness of Orussia in search of alien invaders. However, one of the Brave Witches' members suffers severe injuries on her way to the squadron's headquarters, rendering her unable to participate in any operations. As a result, her sister, Hikari Karibuchi, volunteers to take her place. Though not possessing any special abilities or significant magical powers, she is determined to live up to the expectations of her new comrades and prove herself worthy of the name of a Witch. [Written by MAL Rewrite]

Long ago, a goddess descended from Heaven and blessed the desolate land of Gatepia. As a result, gigantic gates appeared, leading to dungeons abundant in "kirakuri," crystals containing the energy needed for the foundation of the world. This led to the formation of various companies of adventurers who would harvest kirakuri from the dungeons. Following his father's disappearance inside one of the biggest gates in Gatepia, Minato is urged by his childhood friend Yutoria to become the president of his father's treasure-hunting company—the Kibou Company. He reluctantly agrees and meets with the other employees: the priest Makoto, the soldier Akari, and the accountant Guide. Thus, Makoto begins his tenure as president. As he and his comrades strive to fulfill various missions and other assorted tasks in order to keep their small company alive, they will uncover the mystery behind their former leader's sudden departure.

Second year high school student Koguma doesn't lead a very interesting life. She has no parents, and no friends nor hobbies to keep her daily life busy. One day, she acquires a second-hand Honda Super Cub motorcycle and rides it to school. As time goes by, not only does Koguma have a new adventurous life, but she also forges precious friendships thanks to her precious little motorcycle.