"Nobunagun" is a science fiction manga series that blends historical elements with futuristic action. The story centers on Sio Ogura, a high school student with a deep fascination for military history, particularly the legendary Japanese warlord Oda Nobunaga. Sio's life takes a dramatic turn when she encounters a mysterious alien force known as the Evolutionary Invasion Objects (EIOs), which threaten humanity. During an attack, Sio discovers she is a "E-Gene Holder," a descendant of a historical figure whose soul can manifest as a powerful weapon. In her case, she channels the spirit of Oda Nobunaga, gaining immense combat abilities.

Sio is recruited by DOGOO, a secret organization dedicated to combating the EIOs using other E-Gene Holders. These individuals, like Sio, possess the souls of historical figures such as Jack the Ripper, Gandhi, and Newton, each granting unique powers. As Sio trains and fights alongside her teammates, she must navigate the challenges of her newfound abilities while uncovering the truth behind the EIOs and their connection to Earth's history.

The narrative explores themes of identity, legacy, and the clash between past and future. Sio's journey is marked by her struggle to reconcile her admiration for Nobunaga with the darker aspects of his legacy, as well as her growth into a capable leader. The series balances intense action sequences with character development, delving into the personal histories and motivations of both the protagonists and antagonists. As the conflict with the EIOs escalates, Sio and her allies face increasingly formidable foes, leading to a climactic battle that tests their resolve and unity.