"Bakufū Slash! Kizna" is a manga series set in a world where humanity faces constant threats from monstrous creatures known as Kizna. These entities emerge from a mysterious dimension and wreak havoc, feeding on human fear and despair. To combat this existential threat, a specialized organization called the Bakufū is established, composed of individuals who wield unique weapons known as Slash Arms. These weapons are imbued with the power to destroy Kizna, but only those with a specific genetic marker can wield them effectively.

The protagonist, a young man named Kaito, is drawn into this conflict after a tragic encounter with a Kizna leaves him orphaned and scarred. Kaito discovers he possesses the rare genetic marker required to wield a Slash Arm, and he joins the Bakufū to seek vengeance and protect humanity. As he trains and battles alongside other members of the organization, Kaito learns more about the origins of the Kizna and the true nature of the Slash Arms. The weapons are revealed to be fragments of a powerful entity that once sealed the Kizna dimension, and their use comes at a cost—each Slash Arm gradually consumes the life force of its wielder.

The narrative explores the dynamics within the Bakufū, including rivalries, alliances, and the moral dilemmas faced by its members. Kaito forms close bonds with fellow warriors, such as the stoic and disciplined Rina, who serves as his mentor, and the enigmatic Shiro, whose past is intertwined with the Kizna. As the story progresses, Kaito uncovers a conspiracy within the Bakufū, revealing that some members are exploiting the Slash Arms for personal gain, risking the stability of the fragile barrier between dimensions.

The plot intensifies as Kaito and his allies confront increasingly powerful Kizna, culminating in a climactic battle to prevent the complete collapse of the dimensional seal. The series delves into themes of sacrifice, redemption, and the cost of power, as Kaito grapples with the burden of his abilities and the choices he must make to protect those he cares about. The story concludes with a resolution that balances hope and tragedy, leaving a lasting impact on the world and its characters.