"Boku no Bōkūgō" is a series centered around a young boy named Shū, who possesses a unique ability to summon a powerful, sentient suit of armor known as the "Bōkūgō." This armor, which appears to have a will of its own, bonds with Shū and grants him extraordinary strength and defensive capabilities. The story unfolds in a world where mysterious creatures called "Kegai" threaten humanity. These creatures are drawn to negative emotions and feed on them, causing destruction and chaos. Shū, alongside his classmates and friends, becomes involved in a battle to protect their world from the Kegai.

The narrative explores Shū's journey as he learns to control and understand the Bōkūgō, which often reacts unpredictably to his emotions. The armor's origins and true nature remain shrouded in mystery, adding an element of intrigue to the plot. Shū's relationships with his peers, particularly his childhood friend Riri and the enigmatic transfer student Kaito, play a significant role in the story. Riri provides emotional support and a grounding presence, while Kaito, who also possesses a Bōkūgō, becomes both a rival and an ally. Their interactions highlight themes of friendship, rivalry, and the struggle to balance personal growth with the responsibilities of wielding such power.

As the series progresses, Shū and his companions face increasingly dangerous Kegai, each encounter revealing more about the creatures' connection to human emotions and the true purpose of the Bōkūgō. The story delves into the psychological toll of battling these entities, as the characters grapple with their own fears, insecurities, and the moral implications of their actions. The narrative builds toward a climactic confrontation that tests the limits of Shū's resolve and the strength of his bonds with those around him. Through its exploration of human emotion, resilience, and the complexities of power, "Boku no Bōkūgō" presents a compelling tale of heroism and self-discovery.