"Grenadier" is a manga series set in a fictional world resembling feudal Japan, blending elements of action, adventure, and comedy with a focus on gunplay and martial arts. The story centers on Yajirō Kojima, a skilled but reckless samurai, and Rushuna Tendo, a mysterious and highly skilled gunfighter known as a "Senshi." Rushuna wields a unique revolver and adheres to a philosophy of resolving conflicts without killing, aiming to bring peace through non-lethal means. Her approach contrasts sharply with Yajirō’s more traditional and aggressive methods, creating a dynamic partnership as they travel together.

The narrative begins with Yajirō encountering Rushuna after she saves him from bandits. Intrigued by her abilities and ideals, he decides to accompany her on her journey. Their travels take them across a war-torn land where they encounter various factions, warlords, and rival Senshi. Rushuna’s mission is to prevent the spread of war by disarming combatants and promoting understanding, though her pacifist methods are often tested by the harsh realities of the world. Yajirō, initially skeptical of her approach, gradually comes to respect her resolve and skill.

Throughout the series, the duo faces numerous adversaries, including other Senshi who have abandoned their non-lethal principles in favor of power and violence. These confrontations highlight the moral and philosophical conflicts at the heart of the story, as Rushuna strives to uphold her ideals while navigating a world increasingly dominated by greed and ambition. The narrative also delves into Rushuna’s mysterious past, revealing her training as a Senshi and the personal sacrifices she has made to pursue her mission.

The manga balances intense action sequences with moments of humor and character development, particularly in the evolving relationship between Rushuna and Yajirō. Supporting characters, such as Teppa Tendo, a young boy who idolizes Rushuna, and Mikan Kurenai, a rival Senshi with a tragic backstory, add depth to the story and provide additional perspectives on the central themes of conflict and redemption. The series concludes with Rushuna and Yajirō continuing their journey, their bond strengthened and their resolve unshaken despite the challenges they face.