The anime series "Twilight" centers on a young protagonist, Kurenai, who lives in a world where humans coexist with supernatural beings known as "Eclipsers." These entities, born from the shadows of human emotions, possess immense power and often disrupt the balance between the two realms. Kurenai, an orphan with a mysterious past, discovers an innate ability to manipulate light, a rare gift that allows her to combat the Eclipsers. Her journey begins when she encounters a rogue Eclipser named Noctis, who defies his kind by protecting humans rather than harming them. Together, they form an unlikely alliance to uncover the truth behind the Eclipsers' origins and the growing threat they pose to both worlds.

As the story progresses, Kurenai and Noctis are joined by a diverse group of allies, including a skilled warrior named Sora, who wields a blade infused with lunar energy, and Aria, a scholar specializing in ancient texts that hold clues to the Eclipsers' existence. The group travels across various regions, each with its own unique challenges and Eclipser manifestations. Along the way, they uncover fragments of a prophecy that suggests Kurenai's light-based powers are key to restoring balance. However, their mission is complicated by the emergence of a powerful antagonist, Umbra, a former human turned Eclipser who seeks to merge the two realms into eternal darkness.

The narrative delves into themes of duality, exploring the interplay between light and shadow, hope and despair, and the blurred lines between good and evil. Kurenai's internal struggle with her identity and the source of her powers becomes a central focus, as she grapples with the possibility that her abilities may be tied to the very force she is fighting against. The series builds toward a climactic confrontation where Kurenai must confront Umbra and make a choice that will determine the fate of both humans and Eclipsers. The resolution ties together the threads of the prophecy, Kurenai's origins, and the true nature of the Eclipsers, leaving room for potential future developments in the story.