"Big Order" is a manga series written and illustrated by Sakae Esuno, known for his work on "Future Diary." The narrative centers around Eiji Hoshimiya, a high school student who possesses a unique ability known as an "Order." This power allows him to alter reality according to his desires, but it comes with significant consequences. Ten years prior to the main events, Eiji used his Order to destroy the world, driven by a wish to avenge his sister's death. However, his sister, Rin Kurenai, survived and now seeks to stop him, believing his actions to be misguided.

The story unfolds in a world where individuals with Orders are both feared and hunted. Eiji's Order is particularly potent, making him a target for various factions, including the government and other Order users. These factions aim to either control or eliminate him to prevent further chaos. Eiji, however, is not alone; he is accompanied by Sena Hoshimiya, a girl who claims to be his sister and also possesses an Order. Their relationship is complex, blending familial bonds with underlying tensions and secrets.

As the plot progresses, Eiji and Sena navigate a treacherous landscape filled with political intrigue, moral dilemmas, and intense battles. The series delves into themes of power, responsibility, and the consequences of one's actions. Eiji's journey is marked by his struggle to reconcile his past mistakes with his desire to protect those he cares about. Along the way, he encounters a diverse cast of characters, each with their own motivations and Orders, adding layers of complexity to the narrative.

The manga is characterized by its fast-paced storytelling, intricate plot twists, and a blend of action and psychological drama. The interplay between Eiji and Sena, along with the evolving dynamics among the various Order users, drives much of the tension and conflict. The series explores the ethical implications of wielding immense power and the personal cost of seeking redemption in a world teetering on the brink of collapse.