"Sacred Seven" is set in a world where certain individuals possess supernatural abilities known as Sacred Seven powers, which manifest as crystalline forms. These powers can be used for both good and evil, depending on the wielder's intentions. The story centers around Aruma, a high school student who struggles with his uncontrollable Sacred Seven power, which has caused him pain and isolation in the past. Aruma's life takes a dramatic turn when he encounters Ruri Aiba, a wealthy and determined girl who seeks his help to combat Darkstone creatures—malevolent beings born from corrupted Sacred Seven energy.

Ruri, along with her loyal butler and a specialized organization, aims to protect the world from Darkstones and harness the potential of Sacred Seven powers for good. Aruma initially resists involvement but is gradually drawn into the conflict as he learns to control his abilities and confronts his inner turmoil. The narrative explores themes of redemption, self-acceptance, and the duality of power, as Aruma battles both external threats and his own dark alter ego, known as "Night."

The series introduces a diverse cast of characters, each with unique Sacred Seven abilities and personal motivations. Ruri serves as a driving force, balancing her leadership role with a compassionate understanding of Aruma's struggles. Other key figures include Fei, a mysterious girl with her own connection to Sacred Seven powers, and Kenmi, a scientist working to understand and neutralize Darkstones. The interplay between these characters adds depth to the story, as alliances are tested and secrets are revealed.

The plot unfolds through a series of battles against increasingly powerful Darkstones, culminating in a confrontation with the true source of the corruption. The story blends action, emotional drama, and supernatural elements, creating a narrative that balances personal growth with high-stakes conflict. "Sacred Seven" presents a cohesive exploration of its central themes while maintaining a focus on character development and the evolving dynamics between its protagonists.