"Kirameki no Lion Boy" centers on Haruto, a high school student with a mysterious past and a unique ability to transform into a lion-like creature under specific emotional triggers. The narrative unfolds in a modern urban setting where supernatural elements subtly intertwine with everyday life. Haruto’s transformation ability is tied to a curse passed down through his family, a legacy he struggles to understand and control. His life takes a dramatic turn when he encounters Aoi, a transfer student with her own hidden connection to the supernatural world. Aoi possesses the ability to sense and manipulate spiritual energy, and her arrival coincides with a surge in strange occurrences in their town.

The plot delves into the growing bond between Haruto and Aoi as they uncover the truth behind the curse and its origins. Their investigation leads them to a secret organization that seeks to exploit Haruto’s powers for their own gain. Along the way, they encounter allies and adversaries, including other individuals with supernatural abilities, each with their own motivations and ties to the overarching mystery. The story explores themes of identity, legacy, and the struggle to reconcile one’s past with their present.

Haruto’s internal conflict is a central focus, as he grapples with the fear of losing control of his powers and the impact it could have on those around him. Aoi serves as both a stabilizing force and a catalyst for his growth, challenging him to confront his fears and embrace his abilities. The dynamic between the two characters evolves from tentative trust to a deep partnership as they face increasingly dangerous threats.

The narrative is structured around episodic encounters with supernatural entities and the gradual unraveling of the curse’s history. Each arc reveals more about the world’s hidden layers, including ancient rituals, forgotten legends, and the true nature of Haruto’s lineage. The story balances action, mystery, and character development, with a focus on the emotional stakes of Haruto and Aoi’s journey. The supporting cast, including classmates and members of the secret organization, adds depth to the story, providing contrasting perspectives on the supernatural and its place in their world.